Record Warmth Marks Spring Equinox in London

London experiences its hottest day of the year to date, reaching 21°C, coinciding with the arrival of spring.

On March 20, 2025, London recorded its highest temperature of the year so far, with the mercury rising to 21°C, surpassing the previous high of 19.7°C noted in Crosby, Merseyside, on March 9. Forecasters from the Met Office reported generally pleasant weather across the UK, with the best sunshine observed in the southern regions.

Craig Snell from the Met Office commented on the favorable conditions, noting that while it was sunnier in the south, northern areas experienced a slightly hazier but generally dry day.

The unseasonably warm weather coincided with the spring equinox, a day when day and night are nearly equal in duration, representing the astronomical start of spring.

Historical data indicates that the highest temperature recorded on a UK spring equinox was 21.5°C back in 1972. While meteorological spring begins on March 1, the equinox marks the shift towards longer daylight hours.

In celebration of the spring equinox, various events took place across the UK. At Stonehenge, many gathered at dawn to witness the first light of the equinox, participating in music and traditional dancing.

The Druid Order, a group adhering to ancient spiritual practices, held a ceremonial gathering at Tower Hill, London, performing rituals dressed in white robes and garlands that symbolize their beliefs rooted in pre-Christian eras.

However, the warm weather brought concerns regarding air quality, leading to a high pollution alert being issued for London.

This marked the first alert of the year as experts from Imperial College projected an increase in particulate pollutants arriving from mainland Europe.

Mayor of London, Sir Sadiq Khan, urged residents to be mindful of pollution, especially those with respiratory conditions such as asthma, encouraging actions such as avoiding engine idling and refraining from burning wood or garden waste.

In addition to air quality concerns, the Met Office released its first pollen count of the season, indicating a high pollen warning for London and the South East.

Certain regions, including the North West of England, West Midlands, and Wales, were classified with a “very high” pollen warning, signaling the onset of allergy season.

Yolanda Clewlow, the Met Office’s UK pollen forecast manager, remarked on the early arrival of tree pollen, particularly birch pollen, which was expected to be prevalent due to favorable conditions in the previous spring and summer.