It was a warm, dry and sunny May in Royston, although no long term records were broken.

However, after a very dry March and April the ensuing severe drought had become a major issue by the end of the month, only very slightly eased by a few showers of rain in the last week.

This resulted in Spring (March/May) 2011 rainfall in Royston being the lowest since rainfall records began in the town in 1853. The Spring rainfall total was 28.4 millimetres, which is only 21% of the 30 Year (1981/2010) average. The next driest Spring in this period was in 1893 when Spring rainfall totalled 36.8 millimetres.

As for May alone, it was the driest May since 1998. The total rainfall for the month was 19.2 millimetres, which is 38% of the 1981/2010 average. The number of "rain days" (0.2 millimetres or more) was 8, with rainfall exceeding 1.0 millimetre on 4 of these days. The highest daily rainfall amount in May was 5.9 millimetres, which occurred on both 26^th and 30^th.

Surprisingly, May contained two days (7^th and 26^th) with thunder, the first thunder since August 2010 and two-thirds the total for the whole of last year.

Rainfall for 2011 to the end of May stood at 133.4 millimetres, which is 60% of the average.

In recent years May has been a consistently warm month, this year being the 14^th May in the last 15 years with an above average mean temperature. The only exception was May 2010, but this month was only 0.2°C below average.

In the event it was the warmest May since 2008 only. The mean daily maximum temperature was 19.0°C, which is 1.7°C above the 1981/2010 average. The mean night minimum temperature was 0.8°C above average at 8.5°C.

The highest temperature recorded in May was 24.0°C on 6^th. This was an unexceptional value and was the lowest absolute maximum temperature in May since 2002. At the other end of the scale the lowest temperature in the month was 0.5°C on both 3^rd and 4^th. On both of these days Royston suffered damaging ground frosts which cut back tender growth in susceptible plants such as potatoes. On 4^th the lowest grass minimum temperature (-3.9°C) of the month was recorded.

The coldest day of the month was 15^th with a maximum temperature of 15.0°C, whilst the warmest night of the month was 7^th/8^th with a minimum temperature of 14.6°C.

The mean earth (30 cms depth) temperature as measured daily at 0900 GMT in May was 14.7°C, peaking at 15.9°C on 26^th and falling to its lowest value of 13.0°C on 4^th.

After the relatively dull start to the year in January and February, May was the 3^rd consecutive sunnier than average month and the second successive month with sunshine well in excess of 200 hours.

Total sunshine in May was 230.7 hours, which is 122% of the 1971/2000 average. The sunniest day of the month was 24^th with 14.6 hours sunshine. No day in May was completely sunless, the dullest day being 17^th with 1.3 hours sunshine.

The mean wind speed in May was 7.4 mph and the maximum wind gust recorded was 40 mph on 23^rd. The highest daily (00/00 GMT) mean wind speed was 12.8 mph on 23^rd and the lowest daily mean wind speed was 2.8 mph on 19^th. The analysis of daily wind directions as observed at 0900 GMT was NORTH 0 days, NE 2, E 1, SE 2, S 6, SW 9, W 7, NW 4 and CALM 0.

The mean MSL air pressure in the month was 1017.1 mB, which is 1.4 mB above the 30 Year (1981/2010) average. The highest and lowest air pressure values in May were 1027.8 mB on 24^th and 1003.4 mB on 26^th respectively.

The mean relative humidity in May was 69.0%. The highest daily (00/00 GMT) mean relative humidity was 88.5% on 30^th and the lowest daily mean relative humidity was 54.9% on 25^th. The absolute lowest relative humidity reading in May was 26% at 1650 GMT on 25^th.

Fog (visibility < 1000 metres @ 0900 GMT) was not observed on any day in May.

It was the warmest Spring on record (1972) in Royston and the driest since at least 1853 (as already mentioned earlier in this report). The mean daily maximum temperature in Spring was 16.6°C, which is 2.7°C above average, The mean night minimum temperature in Spring was 6.4°C, which is 1.0°C above average. Total rainfall was 28.4 millimetres, which is 21% of average. Sunshine in Spring was 34% above average, totalling 593.8 hours.

Met. Observer, Royston (Iceni) Weather Station

5^th June 2011