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| Shannon Airport 1961-1990 averages | | | | | | | | | | | | | |
| TEMPERATURE (degrees Celsius) | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| mean daily max. | 8.2 | 8.5 | 10.5 | 12.7 | 15.3 | 17.9 | 19.4 | 19.2 | 17.2 | 14.2 | 10.4 | 8.9 | 13.5 |
| mean daily min. | 2.6 | 2.7 | 3.6 | 4.8 | 7.3 | 10.1 | 12.0 | 11.7 | 10.1 | 8.0 | 4.5 | 3.6 | 6.8 |
| mean | 5.4 | 5.6 | 7.0 | 8.8 | 11.3 | 14.0 | 15.7 | 15.5 | 13.6 | 11.1 | 7.5 | 6.3 | 10.1 |
| absolute max. | 14.0 | 14.8 | 20.2 | 22.2 | 25.6 | 31.6 | 30.6 | 28.7 | 25.5 | 21.8 | 18.2 | 15.2 | 31.6 |
| absolute min. | -11.2 | -9.8 | -7.8 | -4.1 | -0.9 | 1.5 | 5.2 | 2.9 | 1.3 | -1.4 | -6.1 | -8.3 | -11.2 |
| mean no. of days with air frost | 6.5 | 5.4 | 3.2 | 1.6 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.3 | 3.5 | 5.0 | 25.4 |
| mean no. of days with ground frost | 13.2 | 11.0 | 9.5 | 8.2 | 2.5 | 0.4 | 0.0 | 0.0 | 0.6 | 2.7 | 9.6 | 11.0 | 68.6 |
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| RELATIVE HUMIDITY (%) | | | | | | | | | | | | | |
| mean at 0900UTC | 88 | 87 | 85 | 81 | 77 | 79 | 81 | 83 | 85 | 88 | 88 | 89 | 84 |
| mean at 1500UTC | 82 | 75 | 70 | 65 | 64 | 67 | 68 | 69 | 71 | 77 | 81 | 84 | 73 |
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| SUNSHINE (hours) | | | | | | | | | | | | | |
| mean daily duration | 1.58 | 2.34 | 3.34 | 4.93 | 5.77 | 5.13 | 4.59 | 4.44 | 3.69 | 2.65 | 1.93 | 1.42 | 3.48 |
| greatest daily duration | 7.8 | 9.5 | 11.6 | 13.6 | 15.3 | 15.8 | 15.7 | 14.8 | 11.6 | 9.9 | 8.8 | 7.1 | 15.8 |
| mean no. of days with no sun | 10 | 7 | 5 | 3 | 2 | 2 | 2 | 2 | 3 | 6 | 8 | 11 | 62 |
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| RAINFALL (mm) | | | | | | | | | | | | | |
| mean monthly total | 97.2 | 72.1 | 71.8 | 55.5 | 60.1 | 62.4 | 57.1 | 82.3 | 81.8 | 92.4 | 94.7 | 99.6 | 926.8 |
| greatest daily total | 29.0 | 33.5 | 28.5 | 29.6 | 27.0 | 29.7 | 42.5 | 35.9 | 35.5 | 33.0 | 33.0 | 50.4 | 50.4 |
| mean no. of days with >= 0.2mm | 20 | 16 | 19 | 16 | 17 | 16 | 15 | 18 | 18 | 20 | 19 | 20 | 214 |
| mean no. of days with >= 1.0mm | 16 | 12 | 14 | 11 | 13 | 11 | 10 | 13 | 13 | 15 | 15 | 16 | 160 |
| mean no. of days with >= 5.0mm | 7 | 5 | 5 | 4 | 4 | 4 | 4 | 5 | 6 | 6 | 7 | 7 | 66 |
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| WIND (knots) | | | | | | | | | | | | | |
| mean monthly speed | 10.9 | 11.1 | 11.0 | 9.5 | 9.5 | 8.9 | 8.7 | 8.6 | 9.6 | 10.0 | 9.6 | 10.5 | 9.8 |
| max. gust | 82 | 80 | 65 | 62 | 61 | 57 | 52 | 55 | 93 | 84 | 64 | 81 | 93 |
| max. mean 10-minute speed | 55 | 53 | 44 | 41 | 39 | 42 | 33 | 39 | 60 | 57 | 45 | 51 | 60 |
| mean no. of days with gales | 2.1 | 1.2 | 1.4 | 0.5 | 0.5 | 0.1 | 0.0 | 0.1 | 0.6 | 0.9 | 1.0 | 1.5 | 9.8 |
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| WEATHER (mean no. of days with...) | | | | | | | | | | | | | |
| snow or sleet | 3.4 | 3.2 | 1.8 | 0.6 | 0.1 | 0.0 | 0.0 | 0.0 | 0.0 | 0.1 | 0.3 | 1.5 | 10.9 |
| snow lying at 0900UTC | 0.8 | 0.7 | 0.1 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.1 | 0.3 | 2.0 |
| hail | 3.7 | 3.1 | 4.3 | 2.5 | 1.7 | 0.2 | 0.1 | 0.2 | 0.3 | 1.1 | 1.8 | 2.7 | 21.7 |
| thunder | 0.9 | 0.5 | 0.4 | 0.3 | 0.4 | 0.8 | 0.8 | 0.5 | 0.4 | 0.4 | 0.4 | 0.4 | 6.3 |
| fog | 4.1 | 2.0 | 1.8 | 2.2 | 1.7 | 1.8 | 1.7 | 3.1 | 3.0 | 3.3 | 3.4 | 3.6 | 31.8 |