Very Mild and Wet
Temperatures
The average maximum temperature during December 2023 in Shoreham was 10.5 Celsius (51F), and that was around 1.5 Celsius (<3F) above normal for the time of year. The average minimum temperature was 6.7 Celsius (44F), and that was also close to 1.5 Celsius (<3F) above the December average. Overall, it was the 3rd mildest December in the area since 1880. Only the Decembers of 1934 and 2015 were milder.
The highest temperature recorded during the month was 14.1 Celsius (57F) on the 21st, but the maximum was 13.3 Celsius (56F) on the 9th, and a further 8 days had maxima above 12 Celsius (54F) including 6 out of the last 10 days of the month. The coolest weather occurred at the beginning of the month, with each of the first 7 days having highs below 10 Celsius (50F). Only 3 other days had maxima below 10 Celsius (50F), and just 1 of these days had a maximum below 9 Celsius (48F). On the 13th, the top temperature was 8.7 Celsius (48F). During the first week of December there were 5 days with maxima below 9 Celsius (48F), but only 3 of these days had highs under 8 Celsius (46F). The 5th had a maximum of 6.5 Celsius (44F), with 3.7 Celsius (39F) and 0.1 Celsius (32F) recorded on the 1st and 2nd respectively.
There were several mild nights during December, and on 7 occasions the temperature remained above 10 Celsius (50F). All of the mild nights occurred after mid month. The highest minimum was 11.7 Celsius (53F) on the 25th, but 11.2 Celsius (52F) occurred on the 19th, and 10.9 Celsius (52F) on the 24th. A further 10 nights had minima ranging from 7 to 10 Celsius (45-50F). Only a few cold nights occurred in December. Although 9 nights had minima below 5 Celsius (41F), including 3 nights after mid month, only 5 nights had lows under 4 Celsius (39F). The last of these coldest nights was the 14th, when 2.9 Celsius (37F), the other low temperatures all occurred during the first week and included lows of minus 1.4 Celsius (30F) on the 1st and minus 2.9 Celsius (27F) on the 2nd.
The sea temperature was briefly around 9 Celsius (48F) during the first week, otherwise it 10 or 11 Celsius (50-52F) throughout the month.
Frost
There were 3 air frosts during December, and that was 1 below average. The first 3 nights had air frost, although it was slight on the 2nd with a low of minus 0.9 Celsius (30F) recorded. The 6th had an air minimum of 0.0 Celsius (32F), but a grass frost occurred, 1 of 8 noted during the month. That was 2 below the average. There were grass frosts on 3 consecutive nights commencing on the 14th, but the lowest temperature was only minus 1.1 Celsius (30F) recorded on the 14th. All the other grass frosts occurred during the first 8 nights of December, the lowest temperatures were minus 3.3 Celsius (26F) on the 2nd, and minus 3.9 Celsius (25F) on both the 1st and 6th.
Rain
Rainfall in December amounted to 148.4 millimetres (5.8 ins.), which was around 30% above the monthly average. Measurable rain fell on 24 days, which was 4 days above the average, and wet days (when 1 millimetre (0.04 ins.), or more, of rain falls) numbered 16, which was 1 day above the average. The first day of the month was dry, but precipitation commenced on the evening of the 2nd and continued, almost without break, until the afternoon of the 5th. Daily rainfall totals included 3.6 millimetres (0.14 ins.) on the 2nd, 30.6 millimetres (1.2 ins.) on the 3rd and 7.6 millimetres (0.3 ins.) on the 4th. Further heavy rain at the end of the week resulted in 18.0 millimetres (0.71 ins.) on the 7th and 21.0 millimetres (0.82 ins.) There were no completely dry days during the following week, although the only day when more than 4 millimetres (0.16 ins.) of rain occurred was on the 10th, when 7.6 millimetres (0.3 ins.) were measured. The 16th and 17th were both dry days, and no measurable rain fell on 4 out of the following 6 days. However, on the 19th, heavy rain and drizzle produced a total of 13.0 millimetres (0.51 ins.). The last week of the month stayed unsettled and there was heavy rain at times. Daily totals included 8.2 millimetres (0.32 ins,), 7.8 millimetres (0.31 ins.) and 8.8 millimetres (0.35 ins.) on the 25th, 27th and 30th respectively. Overall, it appears that 2023 was the 3rd wettest year in the area for at least 160 years with a total of 1218.8 millimetres (48 ins.). That was more than 30% above the long-term annual average. The year included 6 months with totals exceeding 100 millimetres (4 ins. ) per month, including each of the last 3 months of the year, which yielded a combined total of 563.6 millimetres (22.2 ins.) of rain.
Hail
Hail around 5-7 millimetres (0.3 ins) in diameter fell during a heavy shower just after midnight on the 31st.
Thunder
Two thunderstorms occurred either side of midnight on the 30th/31st. The centres of the storms appeared to be to the southwest and northwest of Shoreham and 5 thunderclaps were heard.
Snow
There was light snow, followed by moderate freezing sleet (but mostly rain) mid to late evening on the 2nd. The resulting slush remained on the grass until about 0400 hours on the following morning.
Wind
Apart from the occasional interlude of east to southeast winds ahead of Atlantic depressions, mainly at the beginning of December, the month was very much dominated by winds from between southwest and northwest. Winds were strong at times, particularly at the beginning of the second week, and again after the 20th. At Shoreham Airport, south to southeasterly winds peaked at 32 knots (36 mph) in the early hours of the 4th, and winds from a similar direction reached 33 knots (38 mph) on the morning of the 9th, with southwesterly winds also gusting to 33 knots (38 mph) in the afternoon and evening. Southwesterlies gusted to 34 knots (39 mph) on the afternoon of the 10th and the early hours of the 11th. The 21st was the next windy day with west, then northwesterly, winds reaching 35 and 36 knots (40-41 mph) in the early morning and late afternoon respectively. The 24th was windy all day with the highest gust of 38 knots (43 mph) from the west-southwest occurring during the afternoon. Southwesterly gusts of 33 knots (38 mph) occurred early in the evening on the 25th, with southwesterly winds again prominent on the 27th with gusts to 38 knots (43 mph) in the afternoon. The windy conditions continued throughout the 28th, with the top gust of 37 knots (42 mph) occurring during the morning. After a brief lull, west-southwesterly gusts reached 35 knots (40 mph) on the afternoon of the 29th. South to southwesterly winds strengthened on the evening of the 30th, with 37 knots (42 mph) recorded either side of midnight. The 31st was the windiest day of the month with the highest gust of 41 knots (49 mph) occurring in the early hours.
Fog
Although there was sunshine at times, areas of freezing fog were close by through much of that day, with the densest fog occurring close to the river.
Statistics for December 2023
| Reporting Site | Highest Temp | Lowest Temp | Rain Total (mm) | Wettest | Rain days |
| Shoreham A/P | 13.9 | -3.5 | 139 | 29 | 19 |
| Thorney Island | 13.9 | -2.3 | 169 | 33 | 20 |
| Gatwick A/P | 14.1 | -3.8 | 180 | 40 | 20 |
| Herstmonceux | 14.0 | -4.2 | 142 | 39 | 23 |
| Bournemouth (Hurn) | 14.2 | -4.1 | 212 | 43 | 20 |
| Middle Wallop | 14.2 | -4.1 | 196 | 40 | 20 |
| Dieppe | 13.7 | -2.7 | 59 | 13 | 19 |
- Rainfall totals unreliable for all stations