Saturday ‘was hottest December day in Britain EVER’ as mercury soared above 65F in Scottish Highlands where average temperature is freezing at this time of year
- Met Office said provisional maximum of 18.7C (65.7F) was recorded on Saturday
- Reading took place in Highlands hamlet of Achfary thanks to the Foehn effect
- This sees rain fall on one side of mountain and warm air currents form on other
- Meteorologists say experts will now carry out quality control to validate reading
Britain could have had its hottest December day on record this month thanks to a freak rush of tropical air, weather experts said today.
The Met Office said a provisional maximum temperature of 18.7C (65.7F) was recorded in the Scottish Highlands hamlet of Achfary last Saturday.
If the reading on December 28 is validated following quality control by experts, it would be the highest UK temperature officially recorded during any December.
The Met Office said a provisional maximum temperature of 18.7C (65.7F) was recorded in the Scottish Highlands hamlet of Achfary last Saturday
The average temperature for the Highlands at this time of year is 0C (32F) at night.
Meteorologists put the record down to a weather process called the Foehn effect, where rain falls on one side of a mountain and warm air currents form on the other.
When the moist air travels over high ground such as a mountain, it is forced to rise up over the mountain and then condenses, forming cloud and rain.
Rain falls on the top or the windward side of the mountain but the other side is much drier. Dry air heats quicker so as it descends the leeward side it warms up drastically.
If the reading in Achfary (file picture) on December 28 is validated following quality control by experts, it would be the highest UK temperature officially recorded during any December
The previous record for a December day in Britain of 18.3C (64.9F) was recorded on December 2, 1948 in Achnashellach, also in the Highlands.
This year’s high was also the warmest December day since 2016, when 17C (62.6F) was recorded on December 7 at Hawarden, Flintshire.
Before that, the next warmest December temperature was the 16.1C (61F) recorded back in 1925 at Usk, Monmouthshire, and Wistanstow, Shropshire.
In the UK, notable Foehn events tend to occur across the Highlands where the moist prevailing westerly winds encounter high ground along Scotland’s west coast.
Meteorologists have put the record down to a weather process called the Foehn effect (above), where rain falls on one side of a mountain and warm air currents form on the other
This results in a marked contrast in weather – with the west being subjected to wet weather, while the lower lying east enjoys the warmth and sunshine of the effect.
Overnight on Saturday into Sunday, mild air from Africa pushed across the UK, and as the air travelled from the south west over the UK, it rose up and lost its moisture.
This meant the other side of the hills ended up with drier air. Daytime temperatures on Saturday in the UK peaked at 12.9C (55.2F) at Bala in Gwynedd, North Wales.
It comes after the UK recorded its hottest ever temperature in July of 38.7C (101.7F) in Cambridge, beating the previous UK record of 38.5C (101.3F), set in Kent in 2003.