Monday followed the recent pattern of cool and cloudy days that saw the thermometer eventually rise to 15.7C, early in the afternoon at 14.10, limited by lack of sunshine being 3.4C below my 40-year average. The past night was also cool dipping to 9.6C at 00.49 in the early hours of Tuesday due to thickening cloud that arrived.
Tuesday revealed a dreary start to the new day as cloud and variable shower activity are moving towards our area thanks to the recent depression, still in the southern North Sea, that will bring a northwesterly breeze.
In the Weather Records by Month since 1984 section the September data and associated graphs have been updated and corrected. The mean September graph quite clearly shows the increase in the mean temperature for the month since 1984, a significant change since around 1997. The rainfall fall data and associated graph for September has shown a steady mean total for the past fifteen years, the exception being the major change in 2024.
September 2024 review
Two records broken for rainfall
Although the month got off to a very warm start, with a peak of 25.5C on the 1st, the temperatures dropped away on subsequent days.
On the 5th a large depression developed over the Continent that for three days plagued the UK with dark, dreary days with little solar and many hours of rain. A significant total of 26.8mm was logged on the 5th that fell over the previous twenty-four hours. The daytime temperatures were a degree or two below average due to the low, thick cloud.
Frequent thunder was heard on the 6th and in the early hours of the 8th.
We came under the influence of a low-pressure system to the northwest for the next four days that brought much cooler Arctic air from near Iceland, also windier weather. A maximum of 13.8C on the 12th was 5.3C below my 40-year average and the coldest day since 3rd May. The night that followed was very cold for September with the thermometer sinking to 1.0C, being a significant 7.7C below my 40-year average and the coldest night since 25th April. This low briefly produced a ground frost.
High pressure took control of our weather from the 16th that gave us seven dry days with the wind brisk from the northeast. There were many hours of strong sunshine that lifted the thermometer to 22.3C on the 19th, the warmest day since the 1st (25.5C).
As the anticyclone eased away over Scandinavia, during subsequent days, a depression began to take charge of our weather with thunderstorms arriving during the afternoon of the 20th, no thunder with only modest rainfall. However, in the early hours of the 21st a noisy thunderstorm arrived at 05.15 with very heavy rainfall. The daily rainfall amounted to 17.4mm.
A very slow-moving depression covered the country on the 22nd and 23rd producing a large quantity of rainfall with 35.4mm during the 24 hours up to the 08.00 on the 22nd and another 34.0mm to 08.00 on the 23rd. The monthly rainfall at that point exceeded the previous record set in 2006 when 131.9mm was logged for the whole month.
The new September rainfall record was broken again two days later as another 19.9mm daily precipitation was added up to 08.00 on the 26th.
Another depression settled itself right over our area at 06.15 on the 26th with a barometric pressure of 984.7mb, the lowest pressure since 28th March 2024, thus continuing the very unsettled weather.
The month ended with very cool days and nights with ground frost in the early hours of the 28th and 29th as the thermometer briefly dropped to a minimum of 2.2C on both nights, being 6.4C below my 40-year average. The maximum on the 29th was a significant 5.5C below my long-term average due to the persistent thick, low cloud that produced more rainfall.
The rainfall total for September was a record 221.4mm beating the previous high of 131.9mm set in 2006. The wettest day occurred on the 23rd with 43.4mm of precipitation. Not only was this total greater than the previous September record but it also broke the record for the wettest month in the year set in November 2002 with 203.5mm.
It was a cooler than average September being 0.4C below my 40-year average principally due to the numerous cool days, 22 during the month.
Thunder was observed on four days, namely 6th, 8th, 11th and 21st, with radiation fog observed in the River Og valley in the early morning, up to 08.00, on the 17th.
