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| Birr 1971–2000 averages
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| TEMPERATURE (degrees Celsius) | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| mean daily max | 7.9 | 8.4 | 10.1 | 12.3 | 15.2 | 17.6 | 19.6 | 19.2 | 16.8 | 13.5 | 10.1 | 8.5 | 13.3 |
| mean daily min | 2.0 | 2.2 | 3.2 | 4.0 | 6.3 | 9.1 | 11.4 | 11.0 | 9.0 | 6.7 | 3.6 | 2.8 | 5.9 |
| mean temperature | 4.9 | 5.3 | 6.6 | 8.2 | 10.7 | 13.4 | 15.5 | 15.1 | 12.9 | 10.1 | 6.9 | 5.7 | 9.6 |
| absolute max. | 14.3 | 15.5 | 16.8 | 23.7 | 25.7 | 31.2 | 30.8 | 29.4 | 25.6 | 21.3 | 17.5 | 15.3 | 31.2 |
| min. maximum | -3.5 | -0.5 | 2.0 | 4.3 | 6.3 | 10.4 | 12.5 | 11.6 | 9.7 | 6.7 | 1.5 | -2.2 | -3.5 |
| max. minimum | 11.6 | 11.9 | 11.3 | 13.0 | 15.2 | 16.5 | 18.9 | 18.0 | 17.9 | 15.7 | 13.1 | 13.0 | 18.9 |
| absolute min. | -14.6 | -9.4 | -5.9 | -4.7 | -2.3 | -0.3 | 3.1 | 2.0 | -1.0 | -5.2 | -7.2 | -8.6 | -14.6 |
| mean num. of days with air frost | 8.2 | 6.5 | 5.2 | 3.9 | 1.1 | 0.0 | 0.0 | 0.0 | 0.3 | 1.6 | 5.7 | 6.7 | 39.1 |
| mean num. of days with ground frost | 16.0 | 14.0 | 13.0 | 12.0 | 6.0 | 1.0 | 0.0 | 0.0 | 2.0 | 5.0 | 12.0 | 14.0 | 95.0 |
| mean 5cm soil | 3.3 | 3.4 | 5.0 | 8.3 | 12.3 | 15.6 | 16.9 | 15.8 | 12.9 | 9.5 | 5.5 | 4.3 | 9.4 |
| mean 10cm soil | 3.6 | 3.6 | 4.9 | 7.6 | 11.1 | 14.5 | 16.0 | 15.1 | 12.5 | 9.5 | 5.8 | 4.6 | 9.1 |
| mean 20cm soil | 4.2 | 4.3 | 5.7 | 8.1 | 11.3 | 14.6 | 16.2 | 15.6 | 13.3 | 10.4 | 6.8 | 5.2 | 9.6 |
| RELATIVE HUMIDITY (%) | | | | | | | | | | | | | |
| mean at 0900UTC | 89.7 | 89.1 | 87.3 | 82.0 | 77.7 | 78.1 | 80.8 | 84.1 | 86.2 | 88.9 | 90.3 | 90.0 | 85.3 |
| mean at 1500UTC | 82.6 | 76.6 | 71.9 | 65.1 | 64.9 | 66.0 | 67.8 | 68.0 | 70.3 | 76.1 | 81.0 | 84.8 | 72.9 |
| SUNSHINE (hours) | | | | | | | | | | | | | |
| mean daily duration | 1.5 | 2.1 | 2.8 | 4.4 | 5.1 | 4.4 | 4.1 | 4.1 | 3.6 | 2.7 | 1.9 | 1.3 | 3.2 |
| greatest daily duration | 7.4 | 9.3 | 10.6 | 13.3 | 15.1 | 15.7 | 15.2 | 13.6 | 11.3 | 9.7 | 8.1 | 6.6 | 15.7 |
| mean num. of days with no sun | 11.7 | 7.2 | 6.0 | 3.2 | 2.2 | 2.5 | 2.7 | 2.4 | 3.8 | 6.4 | 8.9 | 12.0 | 69.0 |
| RAINFALL (mm) | | | | | | | | | | | | | |
| mean monthly total | 78.9 | 60.5 | 63.4 | 53.2 | 55.3 | 60.4 | 59.1 | 76.2 | 68.1 | 88.4 | 75.5 | 81.4 | 820.6 |
| greatest daily total | 25.6 | 28.0 | 22.0 | 26.3 | 19.7 | 41.1 | 44.5 | 59.1 | 30.4 | 33.8 | 29.7 | 37.5 | 59.1 |
| mean num. of days with >= 0.2mm | 19 | 16 | 19 | 15 | 15 | 15 | 15 | 17 | 16 | 18 | 18 | 18 | 201 |
| mean num. of days with >= 1.0mm | 14 | 12 | 14 | 10 | 11 | 10 | 11 | 12 | 11 | 14 | 13 | 14 | 146 |
| mean num. of days with >= 5.0mm | 5 | 4 | 4 | 3 | 4 | 3 | 3 | 5 | 5 | 6 | 5 | 5 | 52 |
| WIND (knots) | | | | | | | | | | | | | |
| mean monthly speed | 7.9 | 7.9 | 7.7 | 6.4 | 6.0 | 5.7 | 5.6 | 5.4 | 6.1 | 6.9 | 7.0 | 7.7 | 6.7 |
| max. gust | 85 | 77 | 64 | 58 | 55 | 49 | 49 | 46 | 51 | 64 | 60 | 69 | 85 |
| max. mean 10-minute speed | 51 | 38 | 33 | 29 | 29 | 27 | 24 | 27 | 30 | 37 | 34 | 38 | 51 |
| mean num. of days with gales | 0.3 | 0.3 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.2 | 0.8 |
| WEATHER (mean no. of days with..) | | | | | | | | | | | | | |
| snow or sleet | 4.4 | 3.0 | 2.6 | 1.1 | 0.2 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.4 | 2.1 | 13.8 |
| snow lying at 0900UTC | 2.3 | 1.1 | 0.7 | 0.1 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.4 | 4.6 |
| hail | 0.6 | 0.8 | 2.1 | 2.0 | 1.0 | 0.3 | 0.0 | 0.1 | 0.2 | 0.2 | 0.5 | 0.3 | 8.1 |
| thunder | 0.1 | 0.1 | 0.4 | 0.3 | 0.4 | 0.8 | 0.9 | 0.6 | 0.4 | 0.2 | 0.2 | 0.1 | 4.4 |
| fog | 2.4 | 1.4 | 1.6 | 2.1 | 1.2 | 1.1 | 1.6 | 2.6 | 3.0 | 2.5 | 2.1 | 3.4 | 24.9 |