Relief from prolonged heat is arriving across western Europe this week, with more unsettled conditions bringing the chance of rain and a significant drop in temperatures.
Temperatures are expected to fall back towards seasonal norms. Some parts of the UK could see readings around 3C below normal by Thursday. After a scorching summer, and with a drop of more than 15C compared with the previous Thursday's peak, conditions may feel surprisingly chilly.
There are signs that substantial rain could arrive in southern parts of the UK as a cold front moves in from the Atlantic on Monday night into Tuesday.
As of Monday, parts of southern England had endured 62 consecutive days without rainfall, according to observations at a Met Office weather station in Wisley, Surrey. The last recorded rainfall at that location, on 16 June, amounted to just 0.4mm.
More significant weather is expected from Wednesday into the weekend, as low pressure moves across the UK bringing frequent sharp showers and potentially thundery downpours. After such a prolonged dry spell, even a few substantial bursts of rain are expected to make a noticeable difference to the environment.
Continental Europe is also likely to turn wetter as the main cold front moves southwards into France and Germany on Wednesday. Farther south, however, rainfall is likely to be more sporadic, relying heavily on showers and thunderstorms, with that risk rising from Thursday.
While temperatures are subsiding across Europe, the southern United States is experiencing the opposite. Several southern states have extended extreme heat warnings this week, with a significant lack of overnight cooling. Overnight lows are not falling much below 27-28C (low 80s Fahrenheit).
For comparison, the UK's highest overnight minimum during its late June heatwave reached approximately 22-23C.
High humidity is compounding the discomfort and pushing the heat index to levels that have prompted the issuing of extreme heat warnings. The heat index, also known as apparent temperature, is calculated from the combination of air temperature and humidity and is considered a more accurate reflection of how conditions actually feel.
Apparent temperatures of 31-33C are being modelled as overnight lows. The National Weather Service has warned of "dangerously hot conditions", with forecasted daytime heat index values potentially exceeding 46C, particularly across Louisiana and Mississippi.
