Royston (Iceni) Weather Station

Daily Weather Observations - June 2009

The month of June in Royston was warmer, wetter and sunnier than average, but all by relatively modest margins.

Remarkably this was the 10^th consecutive warmer than average June. Taking the 10 years 2000/2009 as a whole the June mean temperature has been 1.2°C above average.

However, June 2009 did not break any records as it was the warmest June since 2007 only. The mean daily maximum temperature in the month was 21.4°C, which is 1.5°C above the 30 Year (1976/2005) average. The mean night minimum temperature was precisely on the 30 Year average at 10.6°C.

The last two days of the month were the warmest with daily maximum temperatures of 28.8°C and 29.0°C respectively. In contrast, on 5^th the lowest daily maximum temperature (13.5°C) of the month occurred.

The coldest night of June was on 4^th, when the temperature dipped to a minimum of 4.7°C. On the same night the lowest grass minimum temperature (1.5°C) of the month occurred. The highest night minimum temperature in June was 15.3°C on both 27^th and 29^th.

The mean earth temperature at 30 cms depth as read at 0900 GMT daily was 17.4°C. The highest earth temperature was 20.2°C on 30^th, whilst the lowest earth temperature recorded was 15.4°C on 8^th, 10^th and 11^th.

After the dry Spring the June rainfall was above normal, but only by 14%. It was particularly dry after 10^th except for a thunderstorm on 26^th when 17.3 millimetres rainfall was recorded, making this day the wettest day of the month. This was a relatively short but intense storm and temporary flooding occurred in Fish Hill and Melbourn Street in Royston.

Total rainfall in June was 57.1 millimetres. The number of "rain days" (0.2 millimetres or more) in the month was 11, with 7 of these days receiving more than 1.0 millimetre rainfall. Rainfall duration in the month was 21.3 hours.

Thunder was heard on 2 days (15^th and 26^th) in June. On the first of these days a funnel cloud was reported as having been seen some 10 km S of the town, and this may have touched down to ground in the village of Hare Street where extensive damage was reported to the garden of one property including the destruction of several beehives.

June commenced with 2 very sunny days and ended in the same vein with 2 very sunny days. All 4 days recorded over 15 hours sunshine. The sunniest day of the month was 30^th with 15.5 hours sunshine, exceeding sunshine on 1^st by just 1 minute. The sunshine total for the month was 210.6 hours, which is 117% of the 1971/2000 average.

It was the sunniest June since 2006, but sunshine this year was as much as 47.9 hours below the June total recorded in 2006. There were no completely sunless days in June, although 6^th came close with only 1 minute of sunshine!

June was a relatively calm month with no high winds being experienced and the maximum gust speed recorded being 33 mph on 17^th. The highest daily (00/00 GMT) mean wind speed recorded was 10.3 mph on 20^th whilst the lowest daily mean wind speed was 1.5 mph on 10^th.

Wind directions with northerly and easterly components were in the ascendancy in June as indicated by the following table of wind directions as observed at 0900 GMT daily: NORTH 2 days, NE 8, E 3, SE 3, S 1, SW 2, W 4 and NW 7.

The mean MSL air pressure in June was 1016.1 mB, which is 1 mB below the 30 Year (1976/2005) average. The highest and lowest pressure values in June were 1028.4 mB on 23^rd and 998.2 mB on 7^th respectively.

The mean relative humidity in June was 72.3%. The highest daily (00/00 GMT) mean relative humidity was 88.8% on 10^th, whilst the lowest daily mean was 60.2% on 2^nd. The absolute lowest relative humidity value in June was 28% at 1520 GMT and 1605 GMT on 2^nd.

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

Richard Barker

Met. Observer, Royston (Iceni) Weather Station

5^th July 2009

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