Royston (Iceni) Weather Station

Daily Weather Observations - July 2008

Temperatures and sunshine were near normal in July in Royston, but it was a wetter than average month.

It was a warmer July than last year but significantly cooler than the very hot July of 2006. The mean daily maximum temperature was 22.5°C, which is 0.2°C above average. The mean night minimum temperature was 0.5°C above average at 13.1°C.

The highest daily maximum temperature recorded in July was 29.1°C on 28^th. In contrast the lowest daily maximum temperature was 16.8°C on 17^th. The lowest night minimum temperature of the month was 9.2°C on 21^st. In the hot spell near the end of the month a night minimum temperature of 17.4°C was recorded on 27^th, the highest such value of the month. The lowest grass minimum temperature in July was 6.0°C on both 21^st and 22^nd.

The mean earth temperature at 30 cms depth as recorded at 0900 GMT daily was 18.4°C. The highest and lowest earth temperature values were 20.5°C and 17.1°C on 29^th and 10^th respectively.

Most of the July rainfall came at the beginning of the month and by 11^th 47.7 millimetres had been accumulated. The remainder of the month was rather dry with only 11.3 millimetres rainfall but the month’s total of 59.0 millimetres was nonetheless 37% above the 1971/2000 average. It was the 9^th wetter than average July in the last 10 years (the exception being July 2005).

The wettest day of the month was 9^th with 15.8 millimetres rainfall. The number of "rain days" (0.2 millimetres or more) was 16, with rainfall equalling or exceeding 1.0 millimetre on 8 of these days.

Thunder was heard on 3 days in July (6^th, 7^th and 11^th).

Rainfall for the period January/July 2008 was 373.1 millimetres, which is 119% of the 1971/2000 average.

It was the 3^rd sunniest July of the last 10 years. Total sunshine was 212.2 hours, which is 111% of the 1971/2000 average. It was sunnier than in July last year (186.4 hours) but sunshine was significantly below the exceptionally sunny July 2006 (297.2 hours).

The sunniest day of the month was 1^st when sunshine of 14.9 hours was recorded. Sunshine exceeded 14 hours on two other days only (21^st and 30^th).

Only 2 days in July were completely sunless (9^th and 17^th).

Winds with a westerly component accounted for 22 days of the month (at 0900 GMT) and it was rather breezy at times. The mean wind speed over the whole month was 4.9 mph.

The highest daily (00/00 GMT) mean wind speed in July was 9.3 mph on 19^th, whilst the lowest daily mean wind speed was 0.9 mph on 23^rd. The highest wind gust speed recorded in July was 37 mph on 19^th.

The analysis of daily wind directions as observed at 0900 GMT was as follows: NORTH 1 day, NE 0, E 2, SE 3, S 3, SW 9, W 8, NW 5 and CALM 0.

The mean MSL air pressure in July was 1009.8 mB, which is 7 mB below the 1976/2005 average. The highest and lowest air pressure values in July were 1024 mB and 991 mB on 23^rd and 7^th respectively.

The mean relative humidity in July was 76.1%. The highest daily (00/00 GMT) mean relative humidity was 96.9% on 9^th, whilst the lowest daily mean relative humidity was 61.8% on 4^th. The absolute lowest relative humidity reading in July was 35% at 1515 GMT on 4^th.

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

Richard Barker

Richard Barker

Met. Observer, Royston (Iceni) Weather Station

4^th August 2008

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