Very cold, the coldest January in the area since 1987. A snowy first half to the month. Temperatures
The average maximum temperature during January 2010 was 4.4 Celsius (40F), and that was 4.0 Celsius (7F) below normal. The average minimum temperature was 0.4 Celsius (32F), and that was 3.1 Celsius (5.5F) below normal.
The highest temperature recorded during January was 9.7 Celsius (50F) on the 17th, and there were only 6 other days during the month when the temperature exceeded 7 Celsius (45F) with all these less cold days occurring during the second half of the month. Between the 1st and 14th the temperature only reached 5 Celsius (41F) once, on the 2nd, but after the 14th there were only 5 other days with maxima below 5 Celsius, with 3 of these cold days occurring during the last week of January. Between the 4th and 13th highest temperatures were around 1 or 2 Celsius (34-36F), but on the 7th the maximum was only 0.3 Celsius (32F).
There were only 2 nights when the minimum temperature stayed above 5 Celsius (41F), the night of the 18th/19th and the 22nd/23rd when the temperature only fell to 6.2 Celsius (43F). Minima were close to, or below, zero throughout the first half of January and again, on several nights, during the last week. Nights were not especially cold, and minima only dipped below minus 3 Celsius (27F) on 5 occasions. The coldest night was the 6th/7th with minus 6.1 Celsius (21F), although there were also 2 nights during the first week when minus 5 Celsius (23F) was recorded.
Frost
There were 13 air frosts during January, and that was 7 more than normal. Of the 13 air frosts, 8 occurred on the first 9 nights of the year, with another 3 observed during the last 5 days of the month. A total of 20 grass frosts were recorded, and that was also 7 more than normal. A grass frost occurred on each of the first 14 nights of the month, but then only 2 more occurred between the 15th and 26th. There were 9 nights when grass temperatures fell below minus 5 Celsius (23F), with the coldest night, the 7th/8th , dipping to minus 9.6 Celsius (15F). There were 3 other nights early in the month when grass minima fell below minus 8 Celsius (18F). Rain
A total of 55.6 millimetres (2.2ins) of rain fell during January and that was very close to the 20-year average. There were only 19 days with measurable rain (or snow) and that was 2 above the average. Wet days (1.0mm/0.04 ins, or more) numbered 12, and that was also 2 days above average. No measurable rain fell during the first 4 days of the month, but thereafter rainfall was fairly evenly distributed through the month. On 4 days, the 5th, 13th, 16th and 28th, rain (or melted snow) totalled over 5 millimetres (0.2 ins). The wettest day was the 16th when 10.9 millimetres (0.4ins) was recorded.
Thunderstorms
There were no thunderstorms in this part of London.
Hail
A brief light shower of small hail occurred early on the afternoon of the 29th.
Snow
Sleet or snow was observed on 11 days during January, 9 days above average. More than half cover of snow was reported on 9 mornings, and that was 8 above the January average. The first snow fell in the form of grains in the early hours of the 1st with thin patches lying in the morning. Further snow flurries in the evening were also visible on the ground the following morning. Snow, moderate at times, fell on the evening of the 5th with 1cm lying on the morning of the 6th. More snow fell on the 6th, becoming heavy for a while in the late afternoon. There were 5cm of lying snow early on the 7th, but only a little light snow fell on the morning of the 7th. There was a light snow shower early afternoon on the 8th but the depth of lying snow slowly decreased to 4cm. There were still 4cm of snow on the 9th, and again on the 10th, despite moderate snow for a while late afternoon on the 9th. Sleet and snow fell on both the 10th and 11th but with the depth decreasing to 3cm on the 11th and to 2cm on the 12th. The 12th was dry but snow early on the 13th led to a total accumulation of 6cm by morning. On the following day it was milder with rain and only 2cm of snow remained. The remaining patches disappeared during the 15th. Sleet fell on the morning of the 20th, and a light snow shower early on the 30th gave a less than half cover dusting that persisted throughout the 31st.. Wind
Variable winds occurred during January but predominantly the direction had a northerly component. Winds were unusually light for January but moderate winds between northwest and northeast prevailed through much of the second week. The highest gust was only 26kn (30mph) on both the 9th and 29th.
Fog
Mist and low cloud settled into fog for a short time mid morning on the 18th.
Monthly figures for January in, and around, London
