Royston (Iceni) Weather Station

Daily Weather Observations - July 2006

July 2006 was a month of weather extremes in Royston, very hot, very wet and very sunny!

The two most notable features of the July weather were the extreme heat over most of the month, and then the one-off event of the severe thunderstorm on 26^th.

Following on from the very warm June the weather became a lot hotter in July, making the month not only the hottest July since at least 1972 when records began at Royston (Iceni) Weather Station, but the hottest month of any name over this period. The mean temperature easily exceeded the mean temperature in the previous two hottest months, August 1997 and July 1983.

The daily maximum temperature failed to reach the 30 Year (1976/2005) daily mean for this element on only one day in July, that is 7^th with a maximum temperature of 21.0°C. This was the lowest daily maximum temperature of the month. The daily maximum temperature exceeded 30°C on no less than 10 days in the month, including a 6 day consecutive period from 17^th to 22^nd.

The mean daily maximum temperature in July was 27.8°C, which is 5.5°C above the 30 Year (1976/2005) average. On 19^th the temperature reached its highest value of the month of 35.2°C, and this was the hottest July day since at least 1972. During the following night the minimum temperature was as high as 20.7°C, making this the second warmest night for any month since at least 1972 (the highest night minimum temperature being 21.1°C on 9^th August 2004). The mean night minimum temperature in July was 15.1°C, which is 2.5°C above average. The lowest temperature recorded in July was 8.4°C on 15^th, whilst the lowest grass minimum temperature was 5.5°C on the same date.

The mean earth temperature at 30 cms depth as observed at 0900 GMT daily was 20.8°C, with a highest value of 22.5°C on 22^nd and a lowest value of 19.3°C on 10^th.

Although July was in reality a very dry month in Royston it will go down in the records as just the opposite due to a spectacular thunderstorm in the evening of 26^th. In a 2 hour period commencing 1820 GMT a total of 75.5 millimetres of rainfall was recorded, and not surprisingly this caused a number of localised flooding problems in Royston. This amount was 81% of the total rainfall for the month and was the highest daily (09/09 GMT) fall in July in Royston since at least 1972, and the second highest daily fall in any month over this period (the highest being 78.1 millimetres rainfall on 22^nd September 1992).

The number of "rain days" in July was 10, yielding a total for the month of 93.4 millimetres, which is 216% of the 1971/2000 average. The number of days with rainfall above 1.0 millimetre was 7. It was the wettest July since 2004 only, however.

Thunder was heard on 4 days in July (4^th, 22^nd, 26^th and 27^th). The only hail observed to fall in the month was in the thunderstorm on 26^th.

July was an exceptionally sunny month and total sunshine of 297.2 hours (155% of the 1971/2000) average) exceeded the previous record (only last month) for any month since 1997 (when sunshine records commenced) by 38.7 hours. The two month sunshine total for June and July was a remarkable 555.7 hours. The sunniest day of the month was 3^rd with 16.1 hours sunshine. No day in July was completely sunless.

July was a clam month overall with a mean wind speed of 1.9 mph. The highest daily (00/00 GMT) mean wind speed was 7.5 mph on 9^th and the lowest 0.1 mph on 28^th. The maximum wind gust speed recorded in the month was 37 mph on 9^th.

The analysis of wind directions as observed at 0900 GMT daily was NORTH 4 days, NE 7, E 3, SE 2, S 2, SW 8, W 3, NW 2 and CALM 0.

The mean MSL air pressure in July was 1016.7 mB, which is very close to the 30 Year (1976/2005) average, the highest and lowest pressure values being 1032 mB and 1003 mB on 14^th and 31^st respectively.

The mean relative humidity in July was 67.2%. The highest daily (00/00 GMT) mean relative humidity value was 84.3% on 10^th, whilst the lowest daily mean was 47.8% on 17^th. The absolute lowest relative humidity reading was 17% at 1405 GMT on 19^th.

Fog (visibility < 1000 metres) was not recorded at the 0900 GMT observation hour on any day in July.

Richard Barker

Richard Barker

Met. Observer, Royston (Iceni) Weather Station

4^th August 2006

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