As we entered the season of Autumn on September 1 – meteorologically speaking – I found the quotation from Percy Shelley (1792-1822) suited well this year: “In the garden, Autumn is indeed the crowning glory of the year, bringing us the fruition of months of thought and care and toil. And at no season, save perhaps in daffodil time, do we get such superb colour effect as from August to November”.
The variability of our weather is often a talking point and September 2015 was no exception. We all realised that the nights were getting cooler, but the statistics confirm just how cool they were.
The daytime mean was 0.8C below the 31-year average, but the nights were 2.5C below. Combining the two I find that the mean for September was 12.2C, which is 1.7C below the long-term average, the coldest September since 1993 and the third coldest I have recorded since my records began in 1984.
We usually enjoy temperatures into the high 20’s for several days in September, but the warmest days were September 11 and 12 with a maximum of 21.1C. As regards the lowest temperatures, we experienced a grass frost on the morning of September 27 with a minimum air temperature of 1.4C.
Turning to rainfall, September 2015 has followed the trend as being drier than average over the past six years. The total precipitation amounted to 52.2mm, which is 84 per cent of the long-term average or 10mm below. There were many days with modest rainfall totals, but just two days, September 14 and 16, produced two thirds of the total with 15.2mm and 19.3mm respectively.
It is interesting to note that the evaporation from the ground, plants and water sources amounted to 53.2mm, which is 1mm greater than the total rainfall for September.
The especially cool nights meant that the soil temperature at a depth of 5cm was 1.3C lower than last year.
The anticyclone that developed over the United Kingdom for the last week brought welcome sunshine, warmer days and increased solar activity. The last eight days produced over 58 hours of strong sunshine and maxima closer to, but not above, the long-term average.
We all enjoy the rich colours of the changing foliage as autumn progresses, so let’s hope that there are more fine days in which to appreciate them with no autumnal gales to prematurely strip the leaves.
