| Casement 1991–2020 averages | |||||||||||||
| TEMPERATURE (degrees Celsius) | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| mean daily max | 8 | 8.5 | 10.3 | 12.4 | 15.4 | 18 | 19.8 | 19.4 | 17 | 13.7 | 10.3 | 8.3 | 13.4 |
| mean daily min | 2.4 | 2.2 | 3.1 | 4.5 | 6.9 | 9.6 | 11.6 | 11.4 | 9.6 | 7.2 | 4.4 | 2.6 | 6.3 |
| mean temperature | 5.2 | 5.3 | 6.7 | 8.5 | 11.2 | 13.8 | 15.7 | 15.4 | 13.3 | 10.4 | 7.4 | 5.4 | 9.9 |
| absolute max. | 15 | 17.2 | 19.8 | 22.4 | 25.7 | 27.6 | 30.9 | 28.9 | 25.2 | 20.2 | 17 | 14.8 | 30.9 |
| min. maximum | -1.9 | -0.7 | -0.6 | 3.8 | 7 | 10.2 | 10.7 | 12.8 | 9.5 | 5.1 | -3.1 | -4.7 | -4.7 |
| max. minimum | 12.1 | 13 | 11.5 | 12.7 | 14.1 | 17.2 | 18.1 | 18.3 | 18.4 | 15.5 | 13.8 | 12.7 | 18.4 |
| absolute min. | -12.4 | -8.1 | -9 | -5.9 | -3.6 | 0.3 | 4.5 | 2.2 | -0.7 | -4.3 | -9.1 | -15.7 | -15.7 |
| mean num. of days with air frost | 6.8 | 7.1 | 5 | 2.9 | 0.8 | 0 | 0 | 0 | 0.1 | 1.1 | 3.7 | 7.3 | 34.8 |
| mean num. of days with ground frost | 13.9 | 13.6 | 12.8 | 10.3 | 4.6 | 0.7 | 0 | 0 | 1.1 | 4.7 | 8.8 | 13.8 | 84.5 |
| mean 5cm soil | 3.9 | 3.9 | 5.5 | 8.9 | 13 | 16 | 17.3 | 16.2 | 13.1 | 9.4 | 6.2 | 4.3 | 9.8 |
| mean 10cm soil | 4.1 | 4 | 5.3 | 8 | 11.7 | 14.8 | 16.2 | 15.3 | 12.8 | 9.4 | 6.4 | 4.6 | 9.4 |
| mean 20cm soil | 4.7 | 4.8 | 6 | 8.4 | 11.7 | 14.7 | 16.3 | 15.7 | 13.5 | 10.3 | 7.3 | 5.3 | 9.9 |
| RELATIVE HUMIDITY (%) | |||||||||||||
| mean at 0900UTC | 88.1 | 88 | 85.1 | 80.2 | 77.4 | 77.6 | 80.2 | 82.6 | 85.4 | 87.1 | 89.4 | 89 | 84.2 |
| mean at 1500UTC | 82.8 | 77.9 | 71.7 | 67.9 | 66.8 | 67.6 | 69.3 | 69.7 | 71.9 | 76.6 | 82.3 | 84.8 | 74.1 |
| SUNSHINE (hours) | |||||||||||||
| mean daily duration | 1.7 | 2.6 | 3.4 | 5.2 | 6.1 | 5.6 | 4.9 | 5 | 4.2 | 3.3 | 2.2 | 1.5 | 3.8 |
| greatest daily duration | 8.1 | 10 | 11.5 | 13.8 | 15.3 | 16 | 15.5 | 14.4 | 12.3 | 10.2 | 8.8 | 7.3 | 16 |
| mean num. of days with no sun | 8.7 | 5.5 | 4.4 | 2.5 | 1.7 | 2.2 | 1.6 | 1.2 | 2.3 | 4.1 | 6.5 | 9.1 | 49.8 |
| RAINFALL (mm) | |||||||||||||
| mean monthly total | 65 | 55.2 | 51.8 | 55.3 | 59.1 | 65.7 | 59.4 | 71.2 | 61.6 | 81.6 | 81.9 | 75.7 | 783.5 |
| greatest daily total | 30 | 35.6 | 34.2 | 41.5 | 36 | 98.5 | 33.7 | 36 | 51.1 | 86.1 | 82 | 46.8 | 98.5 |
| mean num. of days with >= 0.2mm | 17.6 | 15.8 | 15.5 | 14.8 | 15.4 | 14.8 | 16.3 | 16.8 | 14.9 | 16.7 | 17.8 | 17.5 | 193.9 |
| mean num. of days with >= 1.0mm | 12.3 | 11.4 | 10.2 | 10.9 | 10.5 | 10.1 | 11.9 | 11.5 | 10 | 12 | 12.4 | 13.2 | 136.4 |
| mean num. of days with >= 5.0mm | 4.7 | 3.4 | 3.3 | 3.8 | 3.6 | 3.9 | 3.7 | 4.5 | 4.1 | 4.7 | 5.1 | 5.1 | 49.9 |
| WIND (knots) | |||||||||||||
| mean monthly speed | 12.4 | 12 | 11.1 | 9.5 | 9 | 8.4 | 8.4 | 8.7 | 9 | 10.1 | 10.9 | 11.7 | 10.1 |
| max. gust | 80 | 74 | 71 | 59 | 62 | 55 | 45 | 53 | 59 | 64 | 64 | 82 | 82 |
| max. mean 10-minute speed | 57 | 47 | 47 | 43 | 43 | 41 | 31 | 34 | 41 | 46 | 41 | 54 | 57 |
| mean num. of days with gales | 3.3 | 2.4 | 1 | 0.6 | 0.3 | 0.1 | 0 | 0 | 0.2 | 0.8 | 1.2 | 2.6 | 12.6 |
| WEATHER (mean no. of days with..) | |||||||||||||
| snow or sleet | 3.2 | 3.1 | 2.2 | 0.7 | 0.1 | 0 | 0 | 0 | 0 | 0 | 0.6 | 2 | 11.9 |
| snow lying at 0900UTC | 1 | 0.9 | 0.6 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0.1 | 0.7 | 3.4 |
| hail | 1.1 | 1.8 | 2.3 | 2.7 | 1.5 | 0.3 | 0.2 | 0 | 0.1 | 0.1 | 0.5 | 0.7 | 11.3 |
| thunder | 0.1 | 0.1 | 0.2 | 0.6 | 0.8 | 0.9 | 1.2 | 1.1 | 0.4 | 0.4 | 0.1 | 0 | 6.1 |
| fog | 1.7 | 1.4 | 1.8 | 1.3 | 1.1 | 1.1 | 0.9 | 1.4 | 2.6 | 2.3 | 1.8 | 2.2 | 19.8 |