Cold, Wet and occasionally Windy
Temperatures
The average maximum temperature during May 2021 in Shoreham was 15.8 Celsius (60F), and that was about 3 Celsius (5F) below normal for the time of year. The average minimum temperature was 7.7 Celsius (46F), and that was around 1.5 Celsius (3F) below the May average. Overall, it was the coldest May in the area for 6 years.
The highest temperature recorded during the month was 24.1 Celsius (75F), on the 31st, but there were only 2 other days when the temperature rose above 20 Celsius (68F), namely the 29th and 30th, with maxima of 22.8 Celsius (73F) and 20.4 Celsius (68F) respectively. Another 5 days had highs above 17 Celsius (63F), but only 3 of these less cool days occurred before the 27th. There were many cold days (16) with temperatures staying below 15 Celsius (59F), and on 9 of these days, the temperature failed to reach 14 Celsius (57F). This included every day during the first week of May, and on the 1st a high of 12.8 Celsius (55F) was recorded, with 12.1 Celsius (54f) measured on the 5th.
Even though there was plenty of cloud cover during May, nights were still quite cold. Only 8 nights had minima above 10 Celsius (50F), with just 3 of these milder nights having minima above 11 Celsius (52F). the 9th had a low of 12.0 Celsius (54F), with 11.6 Celsius (53F) and 11.9 Celsius (54F) recorded on the 21st and 29th respectively. On most other nights, minima were between 5 and 10 Celsius (41-50F), but there were some colder nights, these all occurring during the first week of May. On 6 of these nights the temperature fell below 4 Celsius (39F), but the only night below 3 Celsius (37F) was the 6th when 1.9 Celsius (36F) was measured.
The sea temperature rose steadily to 12 Celsius (54F) by the third week, and then accelerated to 14 Celsius (57F) by the end of the month.
Frost
No air frost occurred during May but there was a grass frost on 3 nights, the 3rd, 6th and 7th. The lowest grass temperature occurred on the 6th when minus 2.2 Celsius (28F) was recorded.
Rain
Rainfall in May amounted to 56.4 millimetres (2.2 ins.) which was at least 50% above average for the month. Measurable rain fell on 20 days, which is double the average, and wet days (when 1 millimetre (0.04 ins.) or more of rain falls) numbered 12 days, and that was also double the average. During the first 26 days of May, the only completely dry day was the 11th, although several days only had a trace of rainfall. Measurable rain fell on 5 of the first 7 days of the month, with the 11.0 millimetres (>0.4 ins.) falling on the 7th making it the wettest day of the month. On most of the other days, totals were below 5 millimetres (0.2 ins.), although 6 millimetres (0.25 ins.) fell on the 18th, and another 9.4 millimetres (<0.4 ins.) were recorded on the 23rd. The last week of May was generally dry, with only 0.2 millimetres (0.01 ins.) of rain recorded, plus 0.2 millimetres (0.01 ins.) of dew.
Hail
No hail was observed in this part of Shoreham.
Thunder
Two rumbles of thunder occurred during May. The first was during a shower on the afternoon of the 17th, and the second accompanied a light shower early on the evening of the 19th.
Snow
No sleet or snow was observed this month in Shoreham.
Wind
In complete contrast to April, low pressure dominated the weather pattern during May, with winds often quite strong and on a majority of days (17) blowing from between south and west Winds with an easterly component were mainly confined to the end of the second week and the last few days of the month. At Shoreham Airport, southwesterly gusts reached 48 knots (55 mph) on the evening of the 3rd, with 44 knots (50 mph) recorded in the early hours of the 4th. Southwesterly winds gusted to 45 knots (51 mph) on the evening of the 20th, and it then remained windy throughout the 21st causing much salt damage to plants and trees. The highest gust for the day was 49 knots (56 mph) in the late afternoon, but there were many gale-force gusts of 43 knots (49 mph) during the day. Squally gusts from the south reached 39 knots (44 mph) on the evening of the 23rd, and southwesterly gusts peaked at 32 knots (37 mph) early in the evening on the 25th.
Fog
No fog was observed in this part of Shoreham during May.
Statistics for May 2021
| Reporting Site | Highest Temp | Lowest Temp | Rain Total (mm) | Wettest | Rain days |
| Shoreham A/P | 21.2 | -0.5 | 45 | 11 | 19 |
| Thorney Island | 22.3 | -0.1 | 65 | 11 | 18 |
| Gatwick A/P | 24.1 | -1.5 | 100 | 22 | 19 |
| Herstmonceux | 24.3 | 0.0 | 85 | 12 | 22 |
| Bournemouth (Hurn) | 23.1 | -1.6 | 101 | 16 | 22 |
| Middle Wallop | 23.7 | -0.1 | 86 | 14 | 22 |
| Dieppe | 23.6 | 1.2 | 69 | 14 | 20 |