Warm and Rather Wet
Temperatures
The average maximum temperature during September 2020 in Shoreham was 21.0 Celsius (70F), and that was almost 2 Celsius (3.5F) above normal for the time of year. The average minimum temperature was 12.1 Celsius (54F), and that was close to 0.5 Celsius (<1F) above the September normal.
The highest temperature recorded during the month was 28.6 Celsius (83F) on the 15th. This was the warmest September day in the area for at least 55 years. On 2 other days the temperature exceeded 25 Celsius (77F), with 26.3 Celsius (80F) recorded on the 14th, and 25.2 Celsius (78F) on the 16th. A further 17 days had maxima above 20 Celsius (68F). The coolest weather occurred towards the end of the month. Each of the last 8 days of September had maximum temperatures below 20 Celsius (68F), whereas, only the 3rd and 6th had maxima below this value before the 23rd. On 4 days the temperature failed to rise above 18 Celsius (64F); they were the 4 consecutive days beginning on the 24th. The 25th and 27th had highs of 15.5 Celsius (60F) and 15.3 Celsius (60F) respectively, but the coolest day of the month was the 26th with a high of just 14.3 Celsius (58F).
A few warm nights occurred during September. There were 5 nights, scattered throughout the month, when temperatures stayed above 15 Celsius (59F), although only 1 of these warmer nights had a minimum above 17 Celsius (63F). On the 16th, the minimum temperature was 18.7 Celsius (66F). No particularly cold nights occurred during September, although there were 7 nights when the temperature dipped below 10 Celsius (50F). A total of 4 of these cooler nights were in the last week of September. Only 2 of these nights had lows under 8 Celsius (46F). On the 25th a minimum of 6.7 Celsius (44F) occurred, with 7.0 Celsius (45F) measured on the following night.
The sea temperature was around 19 or 20 Celsius (66-68F) for most of the month, falling to 18 Celsius (64F) at the beginning of the fourth week, and then to 16 Celsius (61F) at the end of the month.
Frost
No frost occurred during September. The lowest grass temperature was 3.9 Celsius (39F) on the 24th.
Rain
Rainfall in September amounted to 63.6 millimetres (2.5 ins.). This was around 30% above the monthly average. The first week of September was changeable, but pressure was high and frontal systems weak, so although the 5th was the only completely dry day, the 6th, with 4.8 millimetres of rain, was the only day when more than 0.4 millimetres (0.02 ins.) of rain were recorded. No measurable rain fell between the 7th and 21st, a total of 15 days. Light rain fell on the 22nd, but on the following day heavier rain occurred and 9.6 millimetres (0.4 ins.) were measured. Showers merged into longer spells of rain, heavy at times, on the 24th and the total rain for the day was 25.2 millimetres (1 inch). No measurable rain fell on the following 5 days, but the last day of the month marked the beginning of a major rainfall event which continued into the first few days of October. The rainfall for the 30th was 22.6 millimetres (0.9 ins.)
Hail
No hail was observed in this part of Shoreham during September.
Thunder
There was 1 rumble of thunder in Shoreham during September. That occurred early in the afternoon on the 24th.
Snow
No sleet or snow fell during September.
Wind
September was unusual in that more than half (16) of the days had winds predominately blowing from between west and north. On most days the wind was no more than moderate in strength with the lightest winds mainly occurring during the first half of the month. However, it was breezy at times during the third and fourth weeks. At Shoreham Airport, the first gusts above 30 knots (34 mph) occurred early on the morning of the 24th when southwesterly gusts reached 40 knots (46 mph). This was followed by brisk northwesterly winds on the 25th with 35 knots (40 mph) measured during the afternoon. The last gusts above 30 knots (34 mph) occurred during the 27th, with a northwesterly gust of 34 knots (39 mph) recorded late in the morning.
Fog
There was no fog observed in this part of Shoreham during September.
Statistics for September 2020
| Reporting Station | Highest Temp | Lowest Temp | Rain Total (mm) | Wettest | Rain days |
| Shoreham A/P | 27.1 | 6.5 | 49 | 20 | 8 |
| Thorney Island | 27.3 | 5.5 | 21 | 8 | 9 |
| Gatwick A/P | 29.3 | 4.7 | 29 | 10 | 9 |
| Herstmonceux | 28.7 | 6.5 | 53 | 28 | 12 |
| Bournemouth (Hurn) | 27.5 | 1.3 | 36 | 17 | 9 |
| Middle Wallop | 27.6 | 3.2 | 32 | 15 | 9 |
| Dieppe | 28.5 | 7.7 | 50 | 20 | 12 |