The spring equinox on Thursday could be the warmest day of 2025 and reach “well above average” temperatures, the Met Office has said.

Wednesday’s highest recorded temperature was 18.7C in Northolt, west London. The Met Office meteorologist Simon Partridge said Thursday will be generally dry and fine with plenty of sunny spells, adding: “It will be a little warmer too”.

He said: “The highest temperatures are expected in an area from London and the home counties to southern Midlands. Here we are likely to see 19C or 20C widely, with one or two spots likely to reach 21C.”

The expected rise in temperatures coincides with the spring equinox, which is the first day of astronomical spring. Parts of the UK may be hotter than Barcelona in Spain and Athens in Greece, where highs of 15C and 12C are forecast respectively.

The highest recorded UK spring equinox temperature was 21.5C in 1972, and the Met Office spokesperson, Stephen Dixon, said 2025’s highest temperature is unlikely to top that.

This year has so far peaked at 19.7C in Crosby, Merseyside, on 9 March. Wetter weather will move in on Friday and the weekend will be more unsettled.

Higher pressure to the east of the UK is currently helping to draw warmer air north across the country, Dixon said, adding that the sunshine on Thursday will be only broken by some fair-weather cloud in central parts of England.

Friday will remain warm for many but some rain is expected to move in from the south-west. Showers are forecast to start in Cornwall and gradually travel north-east during that day into parts of Wales and central and southern England. Rain is then expected for much of the country throughout the weekend.

Meteorological spring always starts on 1 March while astronomical spring, or the equinox, begins around 20 March each year.

The other equinox is in September and both mark the sun crossing the equator, rather than being at an angle. Day and night are therefore about the same length.