Weather in South London during August 2009
It was the driest August for 6 years and the warmest August for 5 years.
Temperatures
The average maximum temperature was 23.2 Celsius (74F), and that was exactly the same as the 20-year normal, but 2.0 degrees Celsius (3.6F) above the 100-year normal. The average minimum temperature was 13.4 Celsius (56F), again exactly on the 20-year average, but only 1.0 Celsius above the 100-year normal.
The highest temperature recorded during August was 28.4 Celsius (83F), on the19th, but there was only 1 other day, the 5th, when the maximum exceeded 27 Celsius (81F). However, there were 7 more days, spread fairly evenly through the month, when 25 Celsius (77F) was bettered. .There were 2 days when the temperature failed to reach 20 Celsius (68F). The maximum on the 28th was 19.6 Celsius (68F), and the coolest day of the month was the 30th with a high of 18.6 Celsius (66F).
There were several rather warm nights during August, but of the 11 minimum temperatures above 15 Celsius (59F), only 2 of these occurred after mid month. The warmest night of the month was that of the 5th/6th with 17.1 Celsius (63F), but both the first and last nights of August had minima above 16 Celsius (61F). The temperature fell below 10 Celsius (50F) on 5 nights, but apart from a low of 9.0 Celsius (48F) on the night of the 2nd/3rd, all the other chilly nights occurred during the last 10 days of the month. The coolest night was that of the 28th/29th with a minimum value of 8.5 Celsius (48F).
Frost
There were no air or grass frosts during August. A grass minimum of 3.7 Celsius (39F) occurred on the night of the 28th/29th with 2 other nights during the last week when the grass reading was below 5 Celsius (41F).
Rain
A total of 35.7 millimetres (1.4ins) of rain fell during August, and that was over 30% below the long-term average. Measurable rain fell on 9 days, 2 below average, and there were only 5 wet days (1.0mm/0.04 ins, or more) and that was 3 days below average. The wettest day was the 6th with 17.7 millimetres (0.7 ins) and there was only 1 other day, the 12th with 5.9 millimetres, when 5 millimetres (0.2 ins) was exceeded. The rain was skewed towards the first half of the month, with a total of less than 7 millimetres (0.3 ins) recorded after the 12th.
Thunderstorms
No thunderstorms were observed in this part of London during August.
Hail
No hail was observed in this part of South London.
Snow
None reported.
Wind
Gentle or moderate southwesterly breezes predominated, althought the wind was light and variable or southeasterly at times during the first week.. Gusts only exceeded 20 knots (23mph) once during the first 19 days of August, but on 6 further days during the remainder of the month. The highest gust was 27 knots (31mph) from the west-northwest on the 28th.
Fog
None reported in this part of London, but some occurred in more rural areas early on the 14th.
Monthly figures for August in, and around, London
The average maximum temperature was 23.2 Celsius (74F), and that was exactly the same as the 20-year normal, but 2.0 degrees Celsius (3.6F) above the 100-year normal. The average minimum temperature was 13.4 Celsius (56F), again exactly on the 20-year average, but only 1.0 Celsius above the 100-year normal.
The highest temperature recorded during August was 28.4 Celsius (83F), on the19th, but there was only 1 other day, the 5th, when the maximum exceeded 27 Celsius (81F). However, there were 7 more days, spread fairly evenly through the month, when 25 Celsius (77F) was bettered. .There were 2 days when the temperature failed to reach 20 Celsius (68F). The maximum on the 28th was 19.6 Celsius (68F), and the coolest day of the month was the 30th with a high of 18.6 Celsius (66F).
There were several rather warm nights during August, but of the 11 minimum temperatures above 15 Celsius (59F), only 2 of these occurred after mid month. The warmest night of the month was that of the 5th/6th with 17.1 Celsius (63F), but both the first and last nights of August had minima above 16 Celsius (61F). The temperature fell below 10 Celsius (50F) on 5 nights, but apart from a low of 9.0 Celsius (48F) on the night of the 2nd/3rd, all the other chilly nights occurred during the last 10 days of the month. The coolest night was that of the 28th/29th with a minimum value of 8.5 Celsius (48F).
Frost
There were no air or grass frosts during August. A grass minimum of 3.7 Celsius (39F) occurred on the night of the 28th/29th with 2 other nights during the last week when the grass reading was below 5 Celsius (41F).
Rain
A total of 35.7 millimetres (1.4ins) of rain fell during August, and that was over 30% below the long-term average. Measurable rain fell on 9 days, 2 below average, and there were only 5 wet days (1.0mm/0.04 ins, or more) and that was 3 days below average. The wettest day was the 6th with 17.7 millimetres (0.7 ins) and there was only 1 other day, the 12th with 5.9 millimetres, when 5 millimetres (0.2 ins) was exceeded. The rain was skewed towards the first half of the month, with a total of less than 7 millimetres (0.3 ins) recorded after the 12th.
Thunderstorms
No thunderstorms were observed in this part of London during August.
Hail
No hail was observed in this part of South London.
Snow
None reported.
Wind
Gentle or moderate southwesterly breezes predominated, althought the wind was light and variable or southeasterly at times during the first week.. Gusts only exceeded 20 knots (23mph) once during the first 19 days of August, but on 6 further days during the remainder of the month. The highest gust was 27 knots (31mph) from the west-northwest on the 28th.
Fog
None reported in this part of London, but some occurred in more rural areas early on the 14th.
Monthly figures for August in, and around, London
| Place | Maximum | Minimum | Rainfall (mm) |
| C. London | 30.1 | 11.5 | 55 |
| Heathrow A/P | 28.9 | 9.5 | 36 |
| Gatwick A/P | 28.5 | 7.4 | 29 |
| Croydon | 26.9 | 9.1 | 35 |
| Northolt | 28.3 | 8.3 | 42 |
| Farnborough | 27.0 | 7.0 | 41 |
| Stansted A/P | 29.1 | 7.6 | 27 |