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West Islip, New York climate
Cfa Humid subtropical
West Islip has a seasonal cool-temperate climate (Humid subtropical, Köppen Cfa). The hottest month is July with an average daily high near 28°C, while the coldest is January averaging around −4°C at night. Precipitation is fairly even year-round, totalling about 1232 mm.
Temperature & precipitation
Daily high–low temperature range with the monthly average, plus monthly precipitation · 1991–2020 normals · hover a month for the exact figuresClear vs cloudy days
Share of days each month that are clear, partly cloudy or cloudy · 1991–2020 · hover a month for the day countsWest Islip climate normals (1991–2020)
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high (°C) | 3 | 4 | 9 | 15 | 21 | 26 | 28 | 27 | 24 | 17 | 11 | 6 |
| Avg temp (°C) | 0 | 0 | 4 | 10 | 16 | 21 | 24 | 23 | 19 | 13 | 8 | 3 |
| Avg low (°C) | −4 | −4 | 0 | 5 | 10 | 16 | 19 | 18 | 15 | 9 | 4 | −1 |
| Precipitation (mm) | 94 | 78 | 108 | 104 | 99 | 109 | 97 | 110 | 119 | 108 | 88 | 118 |
| Jan – Jun | Jan | Feb | Mar | Apr | May | Jun |
|---|---|---|---|---|---|---|
| Avg high (°C) | 3 | 4 | 9 | 15 | 21 | 26 |
| Avg temp (°C) | 0 | 0 | 4 | 10 | 16 | 21 |
| Avg low (°C) | −4 | −4 | 0 | 5 | 10 | 16 |
| Precipitation (mm) | 94 | 78 | 108 | 104 | 99 | 109 |
| Jul – Dec | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|
| Avg high (°C) | 28 | 27 | 24 | 17 | 11 | 6 |
| Avg temp (°C) | 24 | 23 | 19 | 13 | 8 | 3 |
| Avg low (°C) | 19 | 18 | 15 | 9 | 4 | −1 |
| Precipitation (mm) | 97 | 110 | 119 | 108 | 88 | 118 |
How often — frequency of weather events
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Days with measurable rain (days) | 10 | 9 | 10 | 11 | 12 | 10 | 10 | 10 | 7 | 11 | 9 | 12 |
| Days with high ≥ 32°C (days) | — | — | — | 0.1 | 0.4 | 2 | 6 | 2 | 0.7 | 0.1 | — | — |
| Days with low ≤ 0°C (days) | 23 | 21 | 15 | 2 | — | — | — | — | — | — | 5 | 18 |
| Days with snowfall ≥ 2.5 cm (days) | 2 | 3 | 2 | 0.2 | — | — | — | — | — | — | 0.1 | 2 |
| Jan – Jun | Jan | Feb | Mar | Apr | May | Jun |
|---|---|---|---|---|---|---|
| Days with measurable rain (days) | 10 | 9 | 10 | 11 | 12 | 10 |
| Days with high ≥ 32°C (days) | — | — | — | 0.1 | 0.4 | 2 |
| Days with low ≤ 0°C (days) | 23 | 21 | 15 | 2 | — | — |
| Days with snowfall ≥ 2.5 cm (days) | 2 | 3 | 2 | 0.2 | — | — |
| Jul – Dec | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|
| Days with measurable rain (days) | 10 | 10 | 7 | 11 | 9 | 12 |
| Days with high ≥ 32°C (days) | 6 | 2 | 0.7 | 0.1 | — | — |
| Days with low ≤ 0°C (days) | — | — | — | — | 5 | 18 |
| Days with snowfall ≥ 2.5 cm (days) | — | — | — | — | 0.1 | 2 |
Sky & atmosphere
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cloud cover (%) | 69 | 65 | 62 | 60 | 61 | 57 | 53 | 50 | 51 | 55 | 62 | 68 |
| Clear days (≤ 30% cloud) | 3 | 4 | 6 | 6 | 7 | 7 | 8 | 10 | 10 | 9 | 6 | 3 |
| Partly cloudy days (30–70%) | 12 | 9 | 11 | 10 | 11 | 12 | 13 | 11 | 9 | 10 | 10 | 11 |
| Cloudy days (≥ 70%) | 16 | 15 | 15 | 14 | 13 | 11 | 10 | 10 | 11 | 12 | 14 | 16 |
| Relative humidity (%) | 84 | 83 | 82 | 80 | 81 | 81 | 77 | 76 | 76 | 77 | 79 | 82 |
| Wind speed (km/h) | 13.2 | 12.3 | 11.2 | 9.1 | 7.6 | 7.0 | 6.9 | 7.4 | 9.0 | 10.8 | 11.5 | 12.4 |
| Jan – Jun | Jan | Feb | Mar | Apr | May | Jun |
|---|---|---|---|---|---|---|
| Cloud cover (%) | 69 | 65 | 62 | 60 | 61 | 57 |
| Clear days (≤ 30% cloud) | 3 | 4 | 6 | 6 | 7 | 7 |
| Partly cloudy days (30–70%) | 12 | 9 | 11 | 10 | 11 | 12 |
| Cloudy days (≥ 70%) | 16 | 15 | 15 | 14 | 13 | 11 |
| Relative humidity (%) | 84 | 83 | 82 | 80 | 81 | 81 |
| Wind speed (km/h) | 13.2 | 12.3 | 11.2 | 9.1 | 7.6 | 7.0 |
| Jul – Dec | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|
| Cloud cover (%) | 53 | 50 | 51 | 55 | 62 | 68 |
| Clear days (≤ 30% cloud) | 8 | 10 | 10 | 9 | 6 | 3 |
| Partly cloudy days (30–70%) | 13 | 11 | 9 | 10 | 10 | 11 |
| Cloudy days (≥ 70%) | 10 | 10 | 11 | 12 | 14 | 16 |
| Relative humidity (%) | 77 | 76 | 76 | 77 | 79 | 82 |
| Wind speed (km/h) | 6.9 | 7.4 | 9.0 | 10.8 | 11.5 | 12.4 |
Methodology & sources
Temperature & precipitation — the official 1991–2020 climate normals from NOAA's U.S. Climate Normals, measured at Centerport (NOAA GHCN station USC00301309), about 20 km from the city centre.
Cloud, humidity, wind & sunshine — modelled estimates from NASA POWER, NASA's satellite-and-reanalysis climatology. This is the standard global source for atmospheric variables, which are not measured at most weather stations.