Finland endured exceptionally warm weather in May, with temperatures significantly higher than normal by day and night across large parts of the country. The Nordic nation officially recorded 16 heatwave days, breaking the previous high of 14 set in 2018. According to the Finnish Meteorological Institute, heatwave conditions are defined as days when temperatures reach 25C.
Average temperatures were 3-4C higher than normal in the south and west, and 1-3C above normal in the north and east. At the Hattula Lepaa observation station, 29.9C was recorded on 31 May, made it the warmest day of the month.
The high temperatures were the result of a large and persistent area of high pressure that sat across much of northern Europe, with unusually high temperatures also observed in Norway and Sweden. Human-induced climate change is likely to have played a part, with temperatures about 2C higher than they otherwise would have been in a pre-industrial climate, according to the Finnish Meteorological Institute.
It was also extremely dry, with some areas receiving less than 10% of the normal rainfall. There are fears that any sustained dry and warm weather this summer could bring an increased risk of forest fires and drought. The high temperatures have continued into the first few days of June with temperatures in excess of 20C, but they will return close to or slightly below normal by the end of this week as low pressure takes hold.
Meanwhile, prolonged and deadly heatwave conditions that have killed at least 60 people in Mexico are set to continue. A “heat dome” is behind the extreme temperatures the country has been experiencing for more than a month, with many states observing their highest temperatures on record. A heat dome refers to an area of high pressure that stays in the same place for a protracted period of time, trapping very warm air underneath.
The state of Oaxaca recorded its hottest day, with 48C in Valle Nacional on 26 May. Temperatures hit 34.7C at the Tacubaya Observatory in Mexico City on 25 May – its highest May temperature. The same station also hit 33.6C on 1 June, making it the joint warmest June day recorded in the city.
The high temperatures have had a devastating effect on the wildlife, with birds and bats badly affected. Almost 200 howler monkeys succumbed to the extreme conditions, falling from trees in a state of dehydration in the south-eastern state of Tabasco.
