Records have begun to fall in Western Europe, from Spain to France and Switzerland, as an air mass that originated over the Sahara Desert bakes parts of the continent.
The latest: Temperatures in France have risen to dangerous levels, resulting in a "red," weather warning, the highest level, for the Marseille and Montpellier areas. On Thursday, for the first time on record, the temperature topped out at 41.8 degrees Celsius, (or 107.24°F), according to the UK Met Office. Temperatures are forecast to reach 42-45 degrees Celsius (107-113°F) on Friday.
- France's all-time highest temperature on record is 111°F.
- France, Germany, Czech Republic and Poland have all smashed their previous all-time June temperature records.
The big picture: June temperature records, and possibly even all-time high temperature records, will be broken or threatened in multiple countries through the weekend. This includes popular tourist destinations such as Madrid and Paris.
- Western Europe, like other parts of the globe, has been seeing more frequent and intense heat waves in recent years in a trend that scientists have tied to human-caused global warming.
Details: An early season heat wave of this magnitude can be especially hazardous to public health since people have not yet become accustomed to the heat.
- One of the key variables to watch will be nighttime low temperatures.
- When overnight lows get stuck near or above 80°F, the human body can't efficiently cool off at night, raising the likelihood of heat-related illnesses.
- Nice, France already set a new June record for its warmest overnight low temperature on June 26, with a low of 78.8°F.
- The young, sick and elderly are most at risk from such heat events.
- Severe heat waves are a major concern in Europe, particularly since a 2003 heat wave helped to kill as many as 70,000. As a result, health officials have been proactive in preparing for this event.
What's next: The period from Wednesday through Sunday will feature blistering heat across Spain, Portugal, southern France and Italy, with unusually hot conditions stretching north and eastward into Switzerland, Belgium, the Netherlands and Germany.
- Numerous daily and monthly temperature records are already falling as the hot air mass, known as a Sahara Plume, sets up shop.
- On Wednesday, Poland already set a new June temperature record for the country, as did Germany. A station in Berlin reached 101.5°F, which ranks as Germany's hottest June temperature as well.
- France had its hottest June day on record Wednesday, and the country's all-time high temperature for the country of 44.1°C, or 111.4°F, may be within reach.
- According to weather.com, other countries that could see monthly high temperature records set include: Austria, the Czech Republic, Luxembourg and Switzerland. Each of these countries' record June high temperatures were set during the past two decades.
Between the lines: The heat wave's proximate cause is a traffic jam in the upper atmosphere, with a wavy jet stream pattern dominated by two sprawling areas of high pressure — one over Greenland and another across Europe.
- The pattern, known as a Rex Block, can hold weather systems stagnant for days on end, leading to extreme outcomes.
- The high pressure area over Europe has shattered an all-time record for its intensity.
- Some studies show that highly amplified, slower-moving weather patterns such as this one are becoming more common and severe due to global warming, in part due to the altered temperature balance between the equator and the rapidly warming Arctic.
Context: This heat wave is virtually unheard of this early in the season, and it is occurring in a region with some of the longest-kept temperature records in the world. Numerous studies have shown that the odds of extreme heat events, as well as their severity and duration, are dramatically increasing due to human-caused global warming.
- A recent study published in Earth's Future, found that multiple heat waves around the Northern Hemisphere during the summer of 2018 "would not have occurred without human-induced climate change."
- Another study published in 2017 found that climate change has boosted the odds of record-breaking heat across more than 80% of the surface area of the globe for which reliable observations were available.
- Climate scientists warn that heat waves that are now considered exceptional events will become the norm in coming decades if emissions of planet-warming greenhouse gases are not sharply curtailed.