Rarely is the question asked: is our children learning? - George W Bush
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| Photo 1: Flowering Cherry in Front of Ludlow Castle* |
Today (18th March 2026) was provisionally declared the warmest day of the year so far by the UK Met Office. Temperatures of 20.9 ℃ and 20.2 ℃ were recorded in NW Wales and London, respectively. In Hereford (specifically our back garden), the temperature was 21 ℃ for 3 hours this afternoon (2 - 5 pm)**. Mary reported that lots of people were wearing T-shirts in Hereford City. It certainly was a very pleasant day to work in the garden.
Interestingly, it is fairly unusual for places in NW Wales to be warmer than London, albeit only by 0.7 ℃, due to the large Urban Heat Island (UHI) effect from London's built environment. However, due to the Foehn (Fohn) effect, NW Wales gets its day in the limelight as the warmest place in Britain.
How does the Foehn effect work? In this case, the prevailing wind was from the East. As the moving air hits the Welsh mountain ranges (Brecon Beacons*** and Snowdonia****), it rises & cools causing the water vapour to condense out so that the air becomes drier. As this cool dry air descends on the other (western) side of the mountains, it is compressed (as the altitude drops) and adiabatically warmed. Which is the how and why it was warmest on the NW coast of Wales today.
* Strictly speaking, a small Kojo-No-Mai potted cherry tree in front of a photograph of Ludlow Castle!
** All my Davis Weather Station temperature readings are rounded to the nearest whole number
**** Eryri
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