In a reversal of recent trends April was a cool, dull and very wet month.

Rainfall was undoubtedly the main feature of the April weather. The drought conditions of the last year or so continued for the first half of the month with only 9.6 millimetres rainfall being recorded from 1^st to 15^th. Then rainfall was recorded on every day until the end of the month, accumulating a monthly total of 113.1 millimetres in the process.

This rainfall total was 258% of average making it the wettest April in Royston since 1998, and the second wettest April since at least 1853 when rainfall records commenced in the town. April was also the wettest month of any since August 2010. The wettest day of the month was 28^th with 26.2 millimetres rainfall, and this was the wettest April day since 9^th April 1998 and the wettest day in any month since 25^th August 2010. The number of ‘rain days’ (0.2 millimetres or more) in April was 22, and rainfall exceeded 1.0 millimetre on 18 of these days. Thunder was heard on 2 days (19^th and 26^th) and hail was observed to fall on 4 days (11^th, 20^th, 22^nd and 27^th) in April.

The heavy rainfall continued into May with another 28.4 millimetres on 2^nd.

The cumulative total of rainfall for 2012 to the end of April stands at 198.7 millimetres, which is 115% of average. Whilst this eliminates the rainfall deficit for this year to date there is still along way to go to catch up with last year’s deficit of 193.0 millimetres rainfall.

This April’s temperature regime was in complete contrast to April last year, most notably in that the mean daily maximum temperature in April this year of 13.0°C was 6.2°C lower than in April 2011! However, this was only 0.7°C below average indicating the exceptional warmth of April last year. The mean night minimum temperature of 4.2°C in April was similarly 0.6°C below average. It was the coolest April in Royston since 2001, and marginally cooler than March 2012.

The highest daily maximum temperature recorded in April was 18.3°C on 30^th and surprisingly this was 3.3°C lower than the highest temperature recorded in March. The lowest daily maximum temperature was 8.0°C just 2 days earlier on 28^th.

The lowest night minimum temperature in April was –2.1°C on 6^th. On this date the grass minimum temperature fell to its lowest value of the month (-7.0°C) also. The highest night minimum temperature of the month was 8.1°C on both 26^th and 27^th. The numbers of air and ground frosts in April were 3 and 8 respectively.

The mean earth temperature at 30cms depth as observed at 0900 GMT daily was 9.5°C, which is 0.6°C below average. The earth temperature reached its highest value of 11.0°C on 28^th, and dipped to its lowest value of 8.5°C on 6^th.

April commenced on a sunny note with 21 hours sunshine in the first two days. The sunshine total of 12.3 hours on 1^st was the highest daily sunshine figure of the month. The sunny conditions did not last, however, and only 2 further days (10^th and 30^th) exceeded 10 hours sunshine.

Total sunshine in April was 143.1 hours, which is 92% of average. It was the dullest April in Royston since 2006. The sunshine total fell short of April’s figure last year by the very large margin of 85.6 hours! Only 2 days in April were completely sunless, however.

The mean wind speed in April was 6.4 mph and the maximum wind gust speed recorded was 38 mph on 26^th.^. The highest daily (00/00 GMT) mean wind speed was 12.5 mph on 26^th, whilst the lowest daily mean wind speed was 2.5 mph on 7^th.

The analysis of wind directions as observed at 0900 GMT daily was NORTH 1 day, NE 6, E 0, SE 3, S 3, SW 4, W 7, NW 6 and CALM 0.

The mean MSL air pressure in April was 1003.5 mB, which is 11.5 mB below average. The highest and lowest air pressure values recorded in the month were only 2 days apart, 1026.7 mB on 16^th and 976.9 mB on 18^th respectively.

The mean relative humidity in April was 82.5%. The highest and lowest daily mean relative humidity values were 97.8% on 28^th and 66.8% on 16^th respectively. The absolute lowest relative humidity reading in the month was 41% at 1520 GMT on 16^th.

No fog (visibility < 1000 metres @ 0900 GMT) was observed in April.

Met. Observer, Royston (Iceni) Weather Station

7^th May 2012