Rather wet with a typical mix of winter weather

Temperatures

The average maximum temperature during December 2017 in Shoreham was 8.4 Celsius (47F), and that was very close to normal for the time of year. The average minimum temperature was 3.8 Celsius (39F), and that was  also very close to the December normal.

The highest temperature recorded during the month was 12.6 Celsius (55F) on the 30th. There were no other days with maxima above 12 Celsius (54F), but there were 3 more days with highs above 11 Celsius (52F), and a further 6 days when the temperature exceeded 10 Celsius (50F). The mildest weather was generally during the first week and final fortnight of December, although there  were no especially cold days during the remainder of the month. However, the temperature failed to rise above 5 Celsius (41F) on 3 days. The 9th had a high of 4.2 Celsius (40F) and the 11th had a maximum of 3.3 Celsius (38F). This was the coldest day of the month, but the windy 27th, with a high of 3.9 Celsius (39F), felt just as cold.

There were several mild nights during December and on 6 occasions the temperature stayed above 8 Celsius (46F). Only 1 of these mild nights occurred before the 20th,  and that was on the 6th/7th when a minimum  of 8.8 Celsius (48F) was recorded.  Apart from the 30th/31st, when a low of 8.6 Celsius (48F) was measured, the remainder of the mild nights occurred between the 21st and 25th. This included 3 nights when the temperature kept above 9 Celsius (48F). The highest minimum was 9.3 Celsius (49F) on Christmas Eve night. There were many chilly nights during December, and on 16 occasions the minimum temperature was below 3 Celsius (37F). The coldest nights generally occurred during the second and third weeks of December, with 11 nights between the 8th and 19th having minima below 3 Celsius (37F). The lowest temperature recorded was minus 2.4 Celsius (28F) on the night of the 11th/12th.

The sea temperature was mostly between 9 and 10 Celsius (48-50F).

Frost

There were 6 air frosts in Shoreham during December, but all of these were slight. On the 8th/9th a temperature of minus 1.7 Celsius (29F) occurred, with minus 1.4 Celsius (30F) and minus 1.0 Celsius (30F) on the nights of 16th/17th and 18th/19th respectively.  Consecutive air frosts were logged on the 27th/28th and 28th/29th but the temperatures fell no lower than minus 1.4 Celsius (30F). There were 12  grass frosts during December, with 9 of them occurring between the 9th and 19th. On 3 occasions during this frosty spell the grass temperature fell below minus 5 Celsius (23F), including a low of minus 6.1 Celsius (21F) on the 8th/9th. This grass temperature was matched on the night of the 28th/29th.  

Rain

There were 103.2 millimetres (1.25 ins.) of rain during December and that was over 30% above  average. Rain fell on 22 days, about 6 days above what one would expect at this time of year, and wet days ( rainfall of 1 millimetre (0.04 ins) or more)  amounted to 15 days.  High pressure was prominent during the first few days of the month, and although the weather was often cloudy and damp, amounts of rain during this period were mostly small. This changed on the 9th when rain in the evening became persistent and heavy overnight amounting to 22 millimetres (0.9 ins.) by morning. A further 8 millimetres (0.3 ins.) were measured on the 10th, with a further 15 millimetres accumulating over the following 5 days. Once again, pressure rose, and although occasional rain or drizzle occurred, the period between the 16th and 23rd only produced 4 millimetres (0.15 ins.) of rain. Showers, merging into longer spells of rain, occurred on Boxing Day afternoon, with the rain lasting overnight. A total of 21 millimetres   (0.8 ins.) was measured on the 26th, with a further 25 millimetres (1 in.) of rain falling during the rest of the month. This included over 5 millimetres (0.2 ins.) on 3 consecutive days, the 28th, 29th and 30th.

*A rain day is from 0900-0900 UTC

Snow

Snow fell on 2 days during December. On  the morning of the 11th rain turned to sleet and wet snow for a while in the morning and  settled on some vegetation before quickly thawing.  On the 27th, early rain turned to sleet, then wet snow, around mid morning. It settled for a while, but further rain brought about a steady thaw by late morning.

Hail

There was no hail reported  in Shoreham during December.

Thunder

There was no thunder reported in Shoreham during December.

Wind

December was another ‘north-westerly’ month with winds from that direction dominating on a remarkably high 19 days. On most other days the wind blew from between southeast and southwest. It was frequently windy, especially during the second and last weeks of the month. At Shoreham Airport,  a gust of 38 knots (43 mph) was recorded on the 7th,  53 knots (60 mph) on  the 10th,  35 knots (40 mph) on the 14th,  42 knots (48 mph) on the 25th,  35 knots (40 mph) on the 26th,  40 knots (46 mph) on the 27th, 42 knots (48 mph) on the 29th, and  43 knots (49 mph) on the 31st.

Fog

Fog over the Downs, descended to lower levels at times during the mornings of the 20th and 21st.

Statistics for December 2017