February 2010 was another cold month, which completed the statistics for the winter season. It was the coldest February since 2006 and the sixth coldest recorded here, the mean temperature being 1.1°C below the long-term average. There were seven days when snow fell as flakes or pellets and there was considerable wind chill from 8th – 11th with the lowest being -7° C. There were nine days with air frost, none severe; the lowest was recorded on the 21st when the thermometer fell to -3.2°C. The total rainfall of 66.2mm was 103% of the long-term average and most fell in modest daily amounts, the wettest being the 27th with 10mm. There were just four totally dry days in the month, the lowest since February 1955. During the night of 23rd/24th warm air managed to edge in from the south as the cold air mass, which had dominated our weather for most of the month, eased away.
The temperature at the Earth’s surface, as we know, is a balance between heat energy arriving from the Sun and heat energy escaping from the Earth. This loss is progressive throughout winter until strengthening energy from the sun reverses the trend. Bare soil is a poor conductor of heat, but snow is worse, thus night-time drop in temperature is accentuated when there is snow cover, especially fresh, deep snow. For many years I have kept data on the coldest night of the year and it is proving remarkably consistent. From 1984 to 1996, averaged over the winter months, the coldest night was 13th February. In 1997 the 14th moved into second position and in 1997 it became the coldest on average and has remained in this position ever since. It is more remarkable that although there is approximately 0.1°C or less separating the next six nights, in temperature order, the divergence between first and second is seven times greater, a significant difference.
The past winter was the coldest I have recorded, even beating the severe weather experienced in 1984 and 1985, mainly due to the frequency of sub zero nights rather than depressed day time maxima. The rainfall of 235mm was 97% of the long-term average. However, not all of this precipitation seeped into the aquifers. Due to evapotranspiration, 31mm found its way back into the atmosphere through evaporation from ground and water surfaces, with minimal transpiration from plant material at this time of year.
