JERSEY’S climate could be reclassified as Mediterranean in the future if average temperatures continue to rise, according to a senior meteorologist.
It comes after the Island experienced its hottest summer on record and is set for a week of unseasonably high temperatures.
The average temperature across June, July and August was 20.5°C, according to figures released by Jersey Met. That was 2.8°C above the 30-year average and comfortably surpassed the previous summer record of 19.6°C, set in 2022.
Adrienne Le Maistre, senior meteorologist and forecasting manager at Jersey Met, said: “I would suggest that our climate is still categorised as a northern temperate climate, but it is becoming significantly warmer and generally wetter overall, but with hotter, drier summers becoming more likely.
“This may, in the future, lead to a change in categorisation or how these categories are defined.”
A northern temperate climate is typically defined as having four distinct seasons, warm to hot summers often above 15°C and cool to cold winters.
This summer there were four heatwaves recorded – where temperatures exceed 28°C for three or more consecutive days – and several “tropical” nights where temperatures exceed 20°C.
While Ms Le Maistre stopped short of calling Jersey’s current climate Mediterranean, she said that “2026 in particular,” showed a “significant uptick in a general steadier upward trend”.
Turning to the future, Ms Le Maistre added: “Jersey will continue to become warmer and generally wetter overall, with wetter, milder winters and hotter, drier summers becoming increasingly more likely.”
Matt Winter, senior forecaster at the Jersey Met, said September is carrying on this year’s trend of being “warmer than usual”.
This week, a high pressure system combined with an easterly wind is bringing warmer continental air which is set to push the temperature to 24°C tomorrow.
September has been, compared to the Island’s average, very dry. Normally, 60mm of rain would be expected this month, but by the weekend rainfall figures at not hit half that amount at around 25mm.
Looking to the rest of the year, Mr Winter said that temperatures in October, November and December are likely to be “milder than average”. From late October, he added, the relatively dry weather might “turn” as the long range forecasting models are predicting “more unsettled, wetter, windier and milder” weather.
Environmentalist Bruce Labey, vice-chair of Jersey Trees for Life, said the climbing average yearly temperature were a worrying trend.
Mr Labey said the wildfires that spread across France and Spain this summer are the “first stage” in the Mediterranean becoming akin to a temperate climate.
He said: “So the Mediterranean is becoming desert. The northern temperate region is becoming Mediterranean. Everything is just shifting 200, 300 miles to the north.”
Jersey Trees for Life – a charity which plants and protects trees in Jersey – has already ditched planting native tree species in favour of Mediterranean ones.
