After the rather disappointing cooler and duller than average July and August, the situation was retrieved partially at least with a warm, dry and sunny September.

Temperatures increased dramatically through the last week of September and by 30^th a remarkable (for time of year) day maximum temperature of 28.7°C was achieved. This was the highest temperature recorded in the last week of September since records began at this weather station in 1972.

Also, this temperature has been exceeded in the whole month of September in only 3 previous years (1999, 1991 and 1973) since 1972, and was the highest temperature recorded in September since 11^th September 1999. This unseasonable hot spell continued until 3rd October in which time the September ‘high’ was eclipsed by a maximum temperature of 29.0°C on 1^st October!

At the other end of the scale the lowest temperature recorded in September was 8.0°C on 18^th and the lowest grass minimum temperature recorded was 4.4°C on 15^th. The lowest day maximum temperature of the month was 17.9°C on 7^th, whilst the highest night minimum temperature was 16.5°C on 10^th.

The mean daily maximum temperature in September was 21.4°C, which is 2.2°C above the 30 Year (1981/2010) average. The mean night minimum temperature of 12.3°C was similarly above average, but by the lesser value of 1.4°C. It was the warmest September since 2006.

The mean earth temperature at 30 cms depth as observed at 0900 GMT daily was 15.8°C. This element peaked at 17.4°C on 4^th and fell to its lowest value of 14.7°C on 19^th.

September proved to be yet another dry month in this very dry year and only 15.4 millimetres rainfall was recorded, this being only 29% of the 30 Year (1981/2010) average). Rainfall for 2011 to the end of September stood at 297.0 millimetres (69% of average), indicating a very significant deficiency over this period.

The number of "rain days" (0.2 millimetres or more) in September was 10, with rainfall exceeding 1.0 millimetre on 3 of these days. The wettest day of the month was 4^th with a rather modest 5.4 millimetres rainfall. It was the driest September in Royston since 2009 only.

September commenced on a very sunny note with 12.5 hours sunshine occurring on 1^st (the sunniest day of the month and the sunniest September day since at least 1997) followed by a further 11.4 hours on 2^nd. It also ended with 3 very sunny days from 28^th to 30^th, sunshine totalling 32.9 hours in this period.

Total sunshine in September was 196.6 hours, which is 139% of the 30 Year (1971/2000) average. No day in the month was completely sunless. It was the sunniest September in Royston since 2003 (which had 216.8 hours sunshine).

September was a rather windy month and proved to be the second windiest month (after February) so far this year. The mean wind speed over the whole month was 7.8 mph and the maximum wind gust recorded was 47 mph on 12^th. The windiest day (00/00 GMT) was 12^th with a mean wind speed of 16.1 mph, whilst the calmest day was 15^th with a mean wind speed of 2.1 mph over the 24 hour period.

Wind directions containing a southerly or westerly component accounted for all but two days in the month, as per the following analysis of wind directions as observed daily at 0900 GMT: NORTH 0 days, NE 0, E 1, SE3, S 5, SW 15, W 5, NW 1 and CALM 0.

The mean MSL air pressure in September was 1012.6 mB, which is 3.5 mB below the 30 Year (1981/2010) average. The highest and lowest air pressure values in the month were 1028.9 mB and 998.0 mB on 27^th and 12^th respectively.

The mean relative humidity in September was 78.1%. The highest and lowest daily (00/00 GMT) mean relative humidity values in the month were 85.7% and 67.4% on 27^th and 30^th respectively. The absolute lowest relative humidity reading in September was 32% at 1415 GMT on 30^th.

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

Met. Observer, Royston (Iceni) Weather Station

9^th October 2011

Royston Crow (Corvus Cornix)