April 2011 was a remarkable month for many reasons and broke several records. With high pressure dominating for most of the month and keeping weather fronts from the Atlantic at bay, it proved a very dry and very warm month. It was the warmest April on record with the mean maximum +5.1°C and the mean minimum +2.3°C. The three warmest Aprils that I have recorded occurred in the last five years. On the 23rd another record was broken when I recorded the hottest April day when the thermometer peaked at 26.2°C. There were 26 totally dry days, another record equalling the years of 1984 and 1987. Out of the four wet days only one produced a substantial amount of precipitation, 4.2mm on the 3rd, the remaining three days brought minimal amounts of 0.7mm, 0.4mm and 0.1mm. The total rainfall of 5.4mm (the long-term average is 60mm) was the second lowest for an April only beaten by the drier April of 1984 which produced only 2mm. Set against the minimal rainfall is the figure of over 82mm of moisture lost to the atmosphere through evaporation and transpiration. During April there were no air frosts, which is another record; the previous low was of just two air frosts in 2004 and 2007.
A month which was notable for the lack of rainfall and the number of dry days (21). It was the fifth driest April that I have recorded with a total of 25.9mm, just 43% of the long-tern average. The daytime temperatures at the start of the month were decidedly cool but from 6th were average or above whereas we experienced many cool nights, eight with air frosts, the greatest number since 1997, although none were severe. The mean temperature was 0.5°C above the long-term average, principally due to the warm days in the latter half of the month. The individual day extreme statistics were – warmest day on the 28th with 20.1°C, coldest night on the 17th with -1.4°C and wettest day on the 2nd with 8.0mm.
The start to April was dry and warm but by the 6th pressure was dropping and there followed cloudy and wet days, particularly over the Easter weekend, excepting the Monday, which was glorious. The 15th gave us the warmest day with a maximum of 19.2°C but the following day gave us the wettest with a total of 21.5mm – a third of the rainfall for the whole month. However, as an anticyclone settled over the country we then experienced a dry and very warm period from the 18th to the 23rd. The remainder of the month was cloudy and wet, daytime maxima were close to or above the average but followed by cool nights with air frost on the 28th (-1.1°C) and 28th (-0.9°C).
The rainfall of 68.5mm was 112% of the long-term average. This was the third warmest April I have recorded with a mean of 9.72°C, which is 1.4°C above the long-term average – 1987 was 9.73°C and 2007 was 11.41°C.