The weather pattern flip in the final days of August brought a great refreshment for a large part of Europe. Believe it or not, yet another intense heatwave is around the corner. Starting Monday, a large Heat Dome will build into the western half of the European continent, engulfing France, Benelux, and the UK in extreme heat. This could be record-challenging for September as a new powerful heatwave will intensify throughout the week.
The heatwave will also gradually spread into central and northern Europe as the heat dome expands across a large part of the continent. This featured weather pattern is forecast to dominate Europe for around 7-10 days, possibly through mid-September.
It will result in extremely and significantly anomalous temperatures for many parts of Europe.
Temperatures will reach around 30 °C across England, low 30s over Benelux and Germany into central Europe, while France could once again challenge the +40 °C mark in the coming days. Keep in mind that meteorologically speaking, Europe is now in the first autumn season month, so these forecast temperatures are extremely high for this period.
Below is a good overview of how intense the upcoming heatwave will be; we present this on the Meteogram chart for London, UK. Based on two main global weather models, ECMWF and GFS. A Meteogram chart expands across 14 days, indicating temperature at the 850 mbar level (approximately 1250 meters above sea level) and precipitation.
The long-term average temperature for the first half of September is around 7-8 °C for London at this level. The temperature will be significantly above normal from Monday, Sept 4th through the next weekend, Sept 10th. Particularly on Wednesday, when temperatures will be around 20 °C at this level, 12 degrees C higher than normal.
This is undoubtedly an extreme temperature anomaly for the UK and the rest of western Europe coming up this first week of September. A general rule of thumb translates these temperatures to the ground with roughly 12-14 °C higher values, so expect that peak daytime could surpass +30 °C.
Yes, you have read that correctly. The first week of September will likely bring temperatures back into the low 30s for London and the rest of southern and southeastern England. Thanks to an unusually strong heatwave again intensifying over western Europe.
So, with a strengthening ridge aloft, the heatwave will first spread over France on Sunday into Monday, then expand towards the UK and Ireland, Benelux, and the rest of western Europe until mid-week days. Then, late this week, much higher temperatures are also forecast to develop over the continent’s central and northern parts, including Scandinavia.
Generally, when a long period of stable weather is established, a feature known as the Heat Dome intensifies heat waves underneath; this specific weather pattern brings excessive heat and very high temperatures. Let’s talk about it first.
WHAT IS A HEAT DOME, AND WHY IT BRINGS EXTREME HEAT?
Let’s review the primary background cause that led to the development of major heatwaves in Europe this year. When significant heatwave events occurred in the past, in Europe, the United States, and Canada, the Heat Dome is that feature that brings it. Usually, the heat dome is the main, dominant feature of summer weather patterns on both continents.
We will use a heat dome term when extremely high temperatures develop; here is why.
The upper-level ridge pattern, or very warm air mass in the higher altitudes, which we also know as the Upper High (or blocking High), usually forms the heat dome. This weather pattern brings very high and sometimes record-challenging temperatures for the region underneath.
So, this specific term is used when a broad area of high-pressure parks over a large portion of the continent. Usually, it stays there for several consecutive days or even weeks if the event is particularly stable and extreme.
The heat dome works like a lid on a pot. The extensive dome of heat results in the trapping of a warm air mass at all levels underneath, with sinking layers toward the ground. Therefore, the air mass becomes anomalously warm at the lowest elevations and extremely hot near the surface.
A heat wave, associated with a heat dome, creates stable weather and often arid air mass with minimal chances for precipitation or even clouds as the sinking air parcels in the center of the heat dome result in rising temperatures. This is because the weather pattern develops a so-called Omega blocking High, which reminds us of a Greek alphabet letter.
The example below is this kind of pattern that’s about to develop this week over Europe. The omega-blocking pattern engulfs a large part of the continent, with a central heat dome and a low-pressure system on each side. In this case below, one over the southern Mediterranean and the other over the Azores.
Typically, warmer and drier weather leads to a significantly enhanced wildfire threat due to developing drought or worsening the ongoing, pre-existing, arid conditions. Such examples were wildfires in Europe and the Pacific Northwest in North America in recent years, especially in Greece this summer season.
Heat dome is often also to blame for being responsible for deadly heatwaves worldwide, as scorching and excessive heat lasts for very long. Such heat dome events brought record temperatures in Italy in July and scorching hot +45 °C in Spain and Turkey in August.
The daily average and maximum temperatures under the heat dome are typically significantly above average. When the dome is particularly strong, it challenges or breaks existing historical records, as we have seen globally this year. This becomes particularly striking when this feature develops during early summer or autumn/fall.
MULTIPLE HEATWAVES IN EUROPE THIS YEAR; THE LAST ONE ENDED WITH A DEEP TROUGH ACROSS THE CONTINENT
There were several strong and record-breaking heatwave events in Europe this summer, from Spain and Portugal to France, Italy, the Balkan peninsula with Greece and Turkey. Both July and August were significantly warmer than normal.
For instance, on August 10th, the airport station in Valencia, Spain, smashed its previous August heat record by an astonishing +3.4 °C, ending at +46.8 °C (116.2 °F). Arid air mass and dry winds from the higher elevations helped to set new records after more than 35 years.
This was also one of Europe’s highest temperatures this summer season of 2023. Soon after, extreme heat was reported from Turkey, which has also beat its all-time heat record. For the first time in recorded history, +50 °C (122 °F) was recorded in Hassa (Hatay). It beat the previous Turkish record of +49.1 °C (120.4 °F) from July 2021 (Cizre, Turkey).
At the end of August, a weather pattern over Europe dramatically flipped as a deep upper-level wave grazed into the scorching heatwave. The above satellite image is from last week when the frontal system crossed the European continent from west to east.
We have noted some remarks on it for a better understanding. The system was centered over the northern Mediterranean and Italy, which saw tremendous rainfall (300 to 400+ mm in a couple of days), thanks to high humidity and instability for heavy downpours fueled by a persistent marine heatwave over Liguria and the Adriatic Sea.
In the system’s wake, cold air mass spread, clashing with the extreme heat ahead of the main cold front. Heatwave was still parked over the Balkans. Notice how strong winds dragged the Saharan desert sand/dust particles into the Mediterranean and Greece.
Something else can also be seen in the satellite image. There was a widespread thick smoke cloud from the large wildfires in Canada a couple of weeks ago. Global patterns and associated winds have brought smoke clouds all the way to Europe.
Remember the anecdote about how a butterfly flips its wings and how the weather is affected on the other side of the globe? That’s it. Weather systems around the world are well connected, the global circulation is an active live thing.
Let’s dig into the new, potentially historic September heatwave this week.
DEEP LOW DEVELOPS WEST OF IBERIA, INDUCING AN OMEGA-BLOCKING HIGH INTO WESTERN EUROPE
Over the coming days, the general weather situation in Europe indicates a deep upper low will form over the Iberian peninsula and towards the Azores. Ahead of it on its east, an upper-level ridge will rapidly strengthen. It results in strongly anomalous heights, hinting that a long-lasting period of more stable weather will likely follow.
This will be a textbook Omega blocking pattern we see developing over the European continent this month.
A south-southwesterly flow will establish a significant warm plume between the Low and the developing High into Western Europe. Thus, achieving a much warmer air mass in the following days gradually spread north, expanding into northern and central Europe towards the next weekend.
From Monday into Tuesday, an extremely anomalous air mass will develop over France, Benelux, the UK, and Ireland. The warmest and most anomalous air mass will persist for multiple days until next weekend, gradually spreading further north and east with time.
Through mid-week days, the heat dome and heatwave will continue strengthening, reaching the peak over western European countries. The highest temperatures are forecast over France, Benelux, and the UK.
The 500 mbar chart below represents the general weather picture on Wednesday when a major Blocking High will be established. Its center will be over the North Sea, dominating Europe. Anomalies in the higher altitudes will be significant.
With time, a warm air mass will continue and extend into the late week and the weekend, as much warmer weather is forecasted for Germany, Italy, and the northern Mediterranean, as well over Scandinavia. This will happen because of the very powerful heat dome established aloft.
This will result in temperatures significantly above normal for early September.
HEATWAVE RE-INTENSIFIES INTO FRANCE ON MONDAY, TEMPERATURE IS FORECAST TO REACH NEAR THE 40s AGAIN
With a warm plume developing, the first regions affected will again be western Europe. On Monday, temperatures are forecast to climb into the upper 30s across western France, with peaks potentially reaching the 40 °C mark again. Farther north and east, temperatures are forecast to remain in the upper 20s to low 30s, also across Benelux and northeast Spain.
Temperatures will also get much higher on Tuesday and Wednesday, especially for northern and eastern France. Around 35-38 °C is forecast in the peak afternoon hours.
So, almost all of France’s inland areas are forecast to experience temperatures well above 30 °C again this week; the heatwave will start intensifying on Sunday and extend throughout the first week of September.
HEATWAVE EXPANDS INTO THE UK AND IRELAND AFTER TUESDAY, WITH PEAK TEMPERATURES IN THE 20S OVER IRELAND, LOW 30S IN SOUTHERN ENGLAND
The upper High will gradually expand north on Tuesday and Wednesday, allowing temperatures to warm up significantly across the UK and Ireland. On Tuesday, peak afternoon temperatures are forecast to reach the mid-20s over Ireland and low to mid-20s over Scotland, Wales, and northern England. Even higher, up to 27 °C across the south-central England.
With mid-levels becoming even warmer on Wednesday, hot temperatures are forecast to overspread England. The maximum temperatures are likely to surpass +30 °C across southern and southeastern parts of England, which is extremely high for the month of September.
Temperatures over Ireland could also reach around +25 °C on Wednesday. On both days, 22-24 °C over Northern Ireland, Scotland, Wales, and Northern England.
Above normal temperatures are forecast to remain very high also into the second half of this week as the heatwave continues until the next weekend.
EXTENSIVE HEATWAVE FORECAST TO CONTINUE INTO THE NEXT WEEKEND, EXPANDS EAST AND NORTH
In the chart below, we are reviewing the late this week’s mid-range trends. The general weather model consensus agrees that the powerful heat dome will expand the heatwave far north into Scandinavia. Temperatures at all levels are forecast to significantly rise and expand across most of northern Europe.
A large heat dome will be established over the northern half of the European continent. We can see that the blocking High will be parked and centered over Denmark and southern Sweden from Thursday into the weekend, persisting for several days and extending into early next week.
From Wednesday through Sunday, hot weather is forecast to return to Germany, with the highest temperatures reaching the low 30s across the country’s northern half and on the west and southwest on Wednesday, when peak temperatures will develop further west in France.
Very warm temperatures for early September will gradually develop across central Europe and further east into the Czech Republic, Slovakia, and Poland.
Peaks could approach 30 °C and even surpass in the valleys.
Below is a Meteogram for Stuttgart in western Germany, which reveals how rapid temperature increase is forecast after Monday. From the long-term average around 8-9 °C, it will push close to 20 °C. Thus allowing maximum daytime temperatures to be near 30 °C or above locally. Heatwave will extend for more than a week into the next weekend.
This will also allow the Alpine region to push temperatures around 10-12 °C above normal, which means that higher altitudes over the Alps and the Alpine valleys will be very warm. Expect nighttime temperatures to be significantly higher than normal due to thick warmth into the mid-levels.
Following into the weekend, extremely warm to nearly hot weather is forecast to spread into southern Scandinavia and Denmark. Peak temperatures from Thursday into Saturday will be in the mid-20s across south-central Norway and Sweden, including Finland. Baltic region countries as well.
Even higher temperatures are locally expected, especially across portions of southern Sweden where peak afternoon temperatures during the weekend could approach +30 °C.
This is an astonishing high for September so far north! If these temperatures are verified, record-challenging maximum temperatures will likely occur.
HEATWAVE STRENGTHENS INTO ITALY AND THE BALKANS AFTER THURSDAY
Once the heat dome peaks on the west, it will begin to expand eastward after mid-week days. Thus, rising temperatures also into central Europe and the Mediterranean, and re-develop a heatwave.
After Thursday, temperatures will climb back into the low 30s over Italy and the central Balkans, continuing into the weekend.
Maximum temperatures are forecast to be the highest from Saturday through Monday next week for Italy and most Balkan peninsula countries, likely reaching around 35 °C in eastern Croatia, northern Bosnia and Herzegovina, Serbia, and possibly Hungary.
High temperatures will also continue into the rest of the Balkans in the south. Romania, Bulgaria, North Macedonia, Albania, and Greece are forecast to climb back into mid-30s late this week.
BEWARE OF HEALTH RISKS DURING A HEAT WAVE
During an extended period of very warm weather, generally surpassing +35 °C, it is physically challenging and presents an enhanced risk for health.
Sweltering weather, particularly in extended periods – heat waves – is uncomfortable but presents a significant health risk.
Who is most at risk?
Scorching hot weather is uncomfortable for most people. The following groups are particularly threatened by the very high temperatures we encounter during heat waves:
- elderly people aged over 75 years
- babies, young children
- people with chronic/long-term health conditions, such as diabetes, respiratory disease, circulatory disease
- People who are obese
- People taking certain medicines
- people who work outdoors, in hot/poorly ventilated areas, or engage in physical activity in hot weather
- socially isolated people
- people who are not acclimatized to hot weather, such as tourists from northern countries
Always stay cool, hydrated, and healthy in scorching hot weather
Staying hydrated is one of the most crucial things during extreme heat. Consider taking these precautions and measures to stay healthy in scorching weather:
- Drink plenty of water! – A human’s body cools through sweating; on a sweltering day, an adult may lose up to several liters of water. Keep drinking water, and avoid drinking alcohol, hot drinks, and drinks with high sugar content, as they can worsen dehydration. A regular intake of water is a good way of preventing dehydration.
- Keep your body cool; stay out of the sun if possible. Eat small meals, preferably fruit, and salads. Wear light-colored and loose clothing made from natural materials like cotton. Take a cool shower or a cold bath if you feel hot. Also – keep your workspace and living space cool. If you do not have air conditioning, shut the curtains and blinds during the day. Stay in the coolest room, and avoid using the stove and oven as much as possible. If your home gets too hot, go to a cooler place – a library, shopping center, cinema, or swimming pool.
- Keep your food safe! – Keep food that needs refrigeration adequately stored! Food spoils rapidly at high temperatures, and you may risk food poisoning if the food is not stored correctly.
- If you need to go out in the sun – protect your skin and use proper sunscreen and clothing to avoid sunburns. Cover your head correctly.
- Know your body and have a plan – Ask your doctor if you have any health conditions that may increase the risk of heat-related illness. Call and consult with your doctor if you are feeling unwell. Call emergency help (know the number!) if you feel unwell!
Common heat-related illnesses with symptoms: What to do if it happens?
WHO considers these symptoms’ descriptions and treatments below as informative only – consult with your doctor for details and professional advice:
Dehydration
Dehydration occurs when the body loses too much water to maintain normal functions. Symptoms include dizziness, tiredness, irritability, thirst, dark yellow urine, loss of appetite, and fainting. Drink plenty of water or diluted fruit juice. Avoid coffee, alcohol, and sugary drinks. Move to a cooler space to cool off. If you feel unwell, call your doctor or emergency room.
Heat rash
Heat rash is an itchy rash caused by excessive sweating. Move to a cooler, dryer environment, and keep the affected areas dry. Hydrating creams may make the condition worse. Consult with your doctor.
Heat cramps
This happens during strenuous activity when the body sweats and loses water and salt. Heat cramps manifest as muscle pains or spasms. If this happens, stop all activity, move/lie down in a cool place, and raise your legs slightly. Drink water or diluted juice. Have a cool shower or bath, and apply ice packs. Refrain from returning to strenuous activity for several hours. If heat cramps do not subside, seek medical help.
Heat exhaustion
Heat exhaustion is the condition in response to losing excessive amounts of water and salt due to dehydration. Symptoms include heavy sweating, pale skin, fast and weak pulse, fast and shallow breathing, muscle weakness or cramps, tiredness and weakness, dizziness, headache, nausea or vomiting, and fainting.
If heat exhaustion occurs, the body needs to be cooled and rehydrated by moving to a chilled place, lying down, having a cool shower or bath, and placing cool packs under the armpits, groin, or back of the neck. Rehydration should be done by taking small amounts of cool fluids. Medical help is advised if symptoms do not abate within an hour.
Heat stroke
Heat stroke happens when the body temperature reaches 40.5 °C, a severe and life-threatening condition! Immediate first aid in lowering body temperature is critical, and an immediate call for an ambulance! Find more information on heatstroke here.
High relative humidity during a heatwave can also significantly affect the body, as it also becomes physically challenging for those working outside. After high rainfall events, strong heating will help evaporate the soaked grounds, resulting in higher humidity than normal as well.
To represent the real feel of scorching hot temperatures and high humidity, we use a Heat Index. These graphics indicate what is the real feel of temperatures based on what the temperature and humidity are.
As we see, when air mass has a temperature around +35 °C, humidity below 60 percent is much less challenging than once the humidity is very high, e.g., above 80 %. Thus, the real feel temperature would be near 50 degrees Celsius.
With even higher temperatures close to the 40s, such sweltering hot air becomes already hard to handle with even lower humidity, 50 to 60 percent.
Stay safe!
Wxcharts, Pivotalweather, and Meteociel provided images used in this article.
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