Mild and Damp
Temperatures
The average maximum temperature during December 2021 in Shoreham was 9.9 Celsius (50F), and that over 0.5 Celsius (1F) above normal for the time of year. The average minimum temperature was 6.4 Celsius (44F), and that was more than 1.5 Celsius (>2F) above the December average.
The highest temperature recorded during the month was 13.2 Celsius (56F) on the 29th, but 12.2 Celsius (54F) was recorded on both the 30th and 31st, and 14 further days had highs above 10 Celsius (50F), including 7 days with maxima above 11 Celsius (52F). There were 7 consecutive days, beginning on the 11th, with highs above 10 Celsius (50F), and 7 out of the last 8 days of December also had maxima above 10 Celsius (50F). The exception was on the 25th when a high of 9.8 Celsius (50F) was recorded. No cold days occurred during December. On 4 occasions the temperature stayed below 7 Celsius (45F), including 3 out of the 4 days between the 19th and 22nd. However, only 1 of the colder days had a maximum below 6 Celsius (43F). That was on the 2nd, when a high of 5.7 Celsius (42F) was measured.
There were many mild nights during December. On both the 30th and 31st minima of 11.4 Celsius (53F) occurred, and during the second week there were 3 nights with minima above 10 Celsius (50f). A further 9 nights had minima between 8 and 10 Celsius (46-50F), with these mild nights mainly clustered around the middle and end of the month. There were no particularly cold nights, although on 6 occasions minima were below 3 Celsius (37F). Only 1 of these colder nights occurred after the 11th. On the 22nd a minimum of 1.2 Celsius (34F) was recorded. A low of 0.4 Celsius (32F) occurred on the 11th, but the other 5 chilly nights all occurred during the first week of December. On the 7th, a minimum of 0.3 Celsius (32F) was measured, but the coldest night of the month was the 3rd with a minimum of minus 0.6 Celsius (31F).
The sea temperature was around 10 or 11 Celsius (50-52F) throughout the month.
Frost
There was only 1 air frost during December, that occurred on the 3rd, but 6 grass frosts occurred. Unsurprisingly, most of the lowest grass temperatures occurred on the same nights as the lowest air temperatures. Lowest values on the grass were minus 4.4 Celsius (24F) on both the 3rd and 22nd, and minus 5.0 Celsius (23F) on the night of the 7th.
Rain
Rainfall in December amounted to 95.4 millimetres (3.8 ins.), which was slightly below average for the month. Measurable rain fell on 20 days, which was about the average, and wet days (when 1 millimetre (0.04 ins.), or more, of rain falls) numbered 15, and that was also close to the average. Rain fell on each of the first 9 days of the month. Some of the rain was heavy and totalled over 50 millimetres (2 ins.). The largest daily totals were 8.8 millimetres (0.35 ins.) on the 6th, 21.4 millimetres (0.8 ins.) on the 7th, and 11 millimetres (0.4 ins.) on the 9th. Thereafter, pressure rose and rain amounts decreased. Between the 10th and 23rd, only 7 millimetres (0.3 ins.) of rain fell, and that included a fall of 4 millimetres (0.16 ins.) on the 11th. In fact, between the 15th and 22nd there was no measurable rain. By way of contrast, each of the last 9 days of the month had some rain, and the festive period was particularly damp and dreary. On the 24th, nearly 13 millimetres (0.5 ins.) of rain fell, with over 8 millimetres (0.3 ins.) recorded on both the 25th and 26th.
Hail
No hail was observed in this part of Shoreham.
Thunder
No thunder was heard in this part of Shoreham.
Snow
No sleet or snow was observed in Shoreham.
Wind
Winds were between southwest and northwest, and often quite strong, during the first 10 days of December, but then high pressure dominated for a while with lighter winds, and a brief spell of northeast winds after mid month. A return of fresh or strong west to southwesterly winds occurred towards the end of the month. At Shoreham Airport, a windy start to the month saw southwesterlies gust to 34 knots (39 mph) soon after midnight on the 1st. Northwesterly winds gusted to 31 knots (35 mph) just before dawn on the 5th, but on the afternoon of the 7th it was southeasterlies that became strong with gusts of 42 knots (48 mph) recorded. A vigorous trough of low pressure was responsible for the strong winds, and the southwesterlies following the passage of the trough became strong overnight, with 42 knots (48 mph) recorded in the early hours of the 8th. The northwesterlies returned early on the 10th with a gust of 35 knots (40 mph) measured, but then high pressure was dominant, and the next strong winds were not until late in the month. On the 28th, southwesterly gusts reached 44 knots (50 mph) at midday, and the remainder of the month was breezy, but no further gusts exceeded 30 knots (34 mph).
Fog
There were many misty days around the middle and end of the month with low cloud cloaking the Downs. On both the 19th and 29th the cloud lowered to the surface at times to produce fog.
Statistics for December 2021
| Reporting Site | Highest Temp | Lowest Temp | Rain Total (mm) | Wettest | Rain days |
| Shoreham A/P | 13.4 | -1.3 | 78 | 14 | 21 |
| Thorney Island | 13.8 | -0.7 | 85 | 15 | 21 |
| Gatwick A/P | 14.4 | -5.1 | 83 | 18 | 20 |
| Herstmonceux | 13.6 | -2.1 | 149 | 26 | 19 |
| Bournemouth (Hurn) | 14.9 | -3.5 | 84 | 11 | 21 |
| Middle Wallop | 14.8 | -2.1 | 80 | 14 | 22 |
| Dieppe | 15.8 | -1.8 | 62 | 18 | 13 |