Royston (Iceni) Weather Station
Daily Weather Observations - June 2001
June 2001 Weather Review
It was a sunny and dry June in Royston, with the mean temperature being fairly close to the long term average.
The most noteworthy aspect of the June weather was the lack of rainfall, particularly the period 16th/30th when only 0.2 millimetres rainfall was recorded. Total rainfall in June was 21.0 millimetres, which is only 42% of the 30 Year (1971/2000) Royston average.
The number of "rain days" (0.2 millimetres or more) in the month was 8, with 1.0 millimetre or more being recorded on 5 of these days The wettest day of the month was 16th with 12.4 millimetres rainfall. Rainfall duration over the whole month was relatively low at 17.2 hours.
It was the second successive June in Royston with rainfall below 50% of normal, and the 7th drier than average June in the last 10 years. However, June was very wet in each of the years 1997, 1998, and 1999.
Thunder was heard on 4 days (15th, 16th, 26th and 27th) in June.
A very warm last week of June managed to lift the mean temperature for the month as a whole to just above the 25 Year (1973/1997) average for Royston. The highest temperature of the month, 27.6°C on 26th, occurred in this period, and was preceded by maximum temperatures of 26.0°C and 27.0°C on 24th and 25th respectively. In contrast, the day maximum temperature on 17th reached only 13.7°C, the lowest day maximum temperature of the month.
The mean daily maximum temperature in June was 20.1°C, which is 0.4°C above average. The mean daily minimum temperature was exactly average at 10.2°C. The lowest temperature recorded in June was 4.0°C on 3rd. This was the lowest temperature recorded in June since 4th June 1991 when a minimum temperature of 3.0°C was recorded.
The lowest grass minimum temperature of the month was 1.6°C on 9th. This was also the lowest grass minimum temperature recorded in June since 1991, when this element dipped to –1.0 °C on 2nd June 1991.
The mean earth temperature at 30 cms depth as measured daily at 0900 GMT was 16.8°C. The highest and lowest earth temperature values were 19.7°C on 27th and 14.6°C on 11th respectively.
Daily sunshine duration values were unexceptional in the first half of June; in fact between 1st and 18th only 1 day (3rd) reached 10 hours sunshine. However, only 1 day (17th) was completely sunless in this period, and this proved to be the only day in the month with no sunshine at all recorded. After 18th matters improved somewhat and 10 hours sunshine was exceeded on a further 6 days by the end of the month.
The sunnier second half of June increased the sunshine total to 216.3 hours for the whole month, this total being 111% of the average. The sunniest day in June was 25th with 15.7 hours sunshine. The next sunniest day was 21st with 14.7 hours sunshine.
The last 4 days of June were rather windy, albeit warm, when the wind direction veered from SE to SW. The windiest day of the month occurred on 29th when a daily (00/00 GMT) mean wind speed of 7.4 mph was recorded. The highest wind gust speed of 32 mph was measured on 30th (this value also occurred on 7th). The calmest day of the month was 12th with a mean wind speed value of 1.3 mph.
The analysis of daily wind directions as observed at 0900 GMT reveals that winds from between south-west and north-west accounted for two-thirds of the days in the month. This analysis in full is as follows: NORTH 1 day, NE 2, E 0, SE 4, S 3, SW 7, W 7, NW 6 and CALM 0.
The mean MSL air pressure for June was 1016.6 mB, which is about average. The highest pressure value recorded was 1028 mB on both 18th and 19th, and the lowest 1002 mB on 16th.
The mean relative humidity for the month was 68.2%. The highest daily (00/00 GMT) mean relative humidity value was 90.7% on 17th, and the lowest daily mean relative humidity was 56.7% on 25th. The absolute lowest relative humidity reading in June was 33% at 1340 GMT on 25th.
In conclusion, June was a quite reasonable first month of the Summer, but did not break any long term records.
Richard Barker
Richard Barker
Met. Observer, Royston (Iceni) Weather Station
6th July 2001
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