Best time to visit Islip
The best time to visit Islip is September, judged on twenty years of weather records and the events worth going for.
Islip, New York, United States
°C
mm
- Average daily high and low
- Precipitation
- Good month
- Best month
- Made good or best by an event
| Month | Average daily high | Average daily low | Precipitation | Verdict |
|---|---|---|---|---|
| January | 4.2 °C / 40 °F | -0.7 °C / 31 °F | 96 mm / 3.8 in | neither best nor good |
| February | 4.4 °C / 40 °F | -0.8 °C / 31 °F | 99 mm / 3.9 in | neither best nor good |
| March | 7.4 °C / 45 °F | 2.5 °C / 37 °F | 115 mm / 4.5 in | neither best nor good |
| April | 11.9 °C / 53 °F | 7.3 °C / 45 °F | 100 mm / 3.9 in | neither best nor good |
| May | 16.8 °C / 62 °F | 12.5 °C / 55 °F | 94 mm / 3.7 in | good month |
| June | 22.1 °C / 72 °F | 18.2 °C / 65 °F | 92 mm / 3.6 in | good month |
| July | 25.8 °C / 78 °F | 22.4 °C / 72 °F | 94 mm / 3.7 in | good month |
| August | 25.3 °C / 78 °F | 21.7 °C / 71 °F | 94 mm / 3.7 in | good month |
| September | 22.3 °C / 72 °F | 18.5 °C / 65 °F | 94 mm / 3.7 in | best month |
| October | 17.4 °C / 63 °F | 13.1 °C / 56 °F | 115 mm / 4.5 in | good month |
| November | 11.9 °C / 53 °F | 7.2 °C / 45 °F | 89 mm / 3.5 in | neither best nor good |
| December | 7.3 °C / 45 °F | 2.7 °C / 37 °F | 134 mm / 5.3 in | neither best nor good |
Good and best months depend on more than temperature, rain and events. How they are chosen
Each activity on this page has its own good and best months, rated on twenty years of daily weather records. Which measures count, and how much, depends on the activity: humidity for exploring outdoors, wind for the beach, hiking and skiing, snow for skiing alone. Between them, the activities are rated on:
- Daytime highs
- Night-time lows
- How warm it feels
- Humidity
- How much of the day is sunny
- Hours of daylight
- Monthly rainfall
- How many days it rains
- Days of heavy rain
- Wind
- Snowfall and days with snow
- Major events, such as festivals
The chart shows the good and best months for exploring outdoors.
The event icon marks a month that an event lifts to good or best, such as a festival or a natural spectacle. Choose “Weather only” in the toolbar to rate the months on weather alone.
Best months by activity
Exploring outdoors
Mild days and nights, mostly dry and bright. The default for 'when should I go'.
- JJanuary: neither
- FFebruary: neither
- MMarch: neither
- AApril: neither
- MMay: good
- JJune: good
- JJuly: good
- AAugust: good
- SSeptember: best
- OOctober: good
- NNovember: neither
- DDecember: neither
- Best
- September
- Good
- May–August, October
Why these months
May · good
In its favour: feels like (high) 16 °C / 61 °F, share of daylight that is sunny 72%, average daily high 16.8 °C / 62 °F, precipitation 94 mm / 3.7 in, days with heavy rain 3.3 days, average daily low 12.5 °C / 55 °F, wet days 10.8 days, relative humidity 76%.
June · good
In its favour: feels like (high) 23.5 °C / 74 °F, average daily high 22.1 °C / 72 °F, share of daylight that is sunny 78%, precipitation 92 mm / 3.6 in, days with heavy rain 3 days, wet days 9.7 days, average daily low 18.2 °C / 65 °F.
Against: relative humidity 78%.
July · good
In its favour: feels like (high) 29 °C / 84 °F, average daily high 25.8 °C / 78 °F, share of daylight that is sunny 83%, precipitation 94 mm / 3.7 in, days with heavy rain 3.1 days, wet days 10.1 days.
Against: average daily low 22.4 °C / 72 °F, relative humidity 78%.
August · good
In its favour: feels like (high) 27.8 °C / 82 °F, average daily high 25.3 °C / 78 °F, share of daylight that is sunny 83%, precipitation 94 mm / 3.7 in, days with heavy rain 3 days, wet days 9.6 days, average daily low 21.7 °C / 71 °F, relative humidity 76%.
September · best
In its favour: feels like (high) 23 °C / 73 °F, average daily high 22.3 °C / 72 °F, share of daylight that is sunny 77%, precipitation 94 mm / 3.7 in, wet days 8.8 days, days with heavy rain 3.1 days, average daily low 18.5 °C / 65 °F, relative humidity 76%.
October · good
In its favour: feels like (high) 15.6 °C / 60 °F, share of daylight that is sunny 73%, average daily high 17.4 °C / 63 °F, precipitation 115 mm / 4.5 in, average daily low 13.1 °C / 56 °F, wet days 10.1 days, days with heavy rain 3.8 days, relative humidity 73%.
Hiking and trekking
Cool enough to climb in, dry enough to enjoy, long enough days.
- JJanuary: neither
- FFebruary: neither
- MMarch: neither
- AApril: best
- MMay: best
- JJune: good
- JJuly: neither
- AAugust: neither
- SSeptember: good
- OOctober: best
- NNovember: best
- DDecember: neither
- Best
- April–May, October–November
- Good
- June, September
Why these months
April · best
In its favour: average daily high 11.9 °C / 53 °F, precipitation 100 mm / 3.9 in, average daily low 7.3 °C / 45 °F, share of daylight that is sunny 73%, daylight per day 13.3 h, wet days 10.5 days, feels like (high) 9 °C / 48 °F, days with heavy rain 3.6 days, wind (daily max) 26 km/h / 16 mph.
May · best
In its favour: average daily high 16.8 °C / 62 °F, precipitation 94 mm / 3.7 in, feels like (high) 16 °C / 61 °F, average daily low 12.5 °C / 55 °F, share of daylight that is sunny 72%, daylight per day 14.5 h, wet days 10.8 days, days with heavy rain 3.3 days, wind (daily max) 23 km/h / 14 mph.
June · good
In its favour: average daily high 22.1 °C / 72 °F, precipitation 92 mm / 3.6 in, wet days 9.7 days, share of daylight that is sunny 78%, daylight per day 15 h, days with heavy rain 3 days, feels like (high) 23.5 °C / 74 °F, wind (daily max) 22 km/h / 13 mph.
Against: average daily low 18.2 °C / 65 °F.
September · good
In its favour: average daily high 22.3 °C / 72 °F, precipitation 94 mm / 3.7 in, wet days 8.8 days, share of daylight that is sunny 77%, daylight per day 12.4 h, feels like (high) 23 °C / 73 °F, days with heavy rain 3.1 days, wind (daily max) 22 km/h / 14 mph.
Against: average daily low 18.5 °C / 65 °F.
October · best
In its favour: average daily high 17.4 °C / 63 °F, precipitation 115 mm / 4.5 in, feels like (high) 15.6 °C / 60 °F, average daily low 13.1 °C / 56 °F, share of daylight that is sunny 73%, wet days 10.1 days, daylight per day 11.1 h, days with heavy rain 3.8 days, wind (daily max) 26 km/h / 16 mph.
November · best
In its favour: average daily high 11.9 °C / 53 °F, precipitation 89 mm / 3.5 in, wet days 8.5 days, average daily low 7.2 °C / 45 °F, share of daylight that is sunny 71%, days with heavy rain 3.1 days, feels like (high) 8.4 °C / 47 °F, wind (daily max) 28 km/h / 17 mph.
Against: daylight per day 9.9 h.
An activity is listed only where it applies: skiing at ski destinations, beach and swimming at beach destinations. The nearest ski area is Mountain Creek, 119 km away.
Weather averages
Monthly averages over twenty years, 2006–2025. Highs, lows and precipitation are in the chart at the top.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Feels like (high) | -0.6 °C | -0.2 °C | 3.2 °C | 9 °C | 16 °C | 23.5 °C | 29 °C | 27.8 °C | 23 °C | 15.6 °C | 8.4 °C | 3 °C |
| Days with heavy rain | 3.1 days | 3.3 days | 3.8 days | 3.6 days | 3.3 days | 3 days | 3.1 days | 3 days | 3.1 days | 3.8 days | 3.1 days | 4.8 days |
| Time rain usually falls | 5 am | 11 am | 11 pm | 1 pm | 3 am | 9 am | 9 am | 7 am | 9 am | 11 pm | 11 pm | 7 am |
| Sunshine per day | 6.8 h | 7.4 h | 8.7 h | 9.7 h | 10.5 h | 11.7 h | 12.2 h | 11.4 h | 9.6 h | 8.1 h | 7 h | 5.9 h |
| Relative humidity | 69% | 69% | 68% | 70% | 76% | 78% | 78% | 76% | 76% | 73% | 69% | 71% |
Sea temperature
Averaged over a shorter period (2022–2025) than the twenty-year averages above.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sea temperature 2022–2025 | 5.5 °C | 4.7 °C | 5.9 °C | 8.8 °C | 13.3 °C | 17.6 °C | 22.5 °C | 21.6 °C | 21.4 °C | 18.1 °C | 13.1 °C | 8.2 °C |
| Sea temperature (daily max) 2022–2025 | 5.6 °C | 4.8 °C | 6.1 °C | 9.1 °C | 13.7 °C | 18.1 °C | 23.1 °C | 22.1 °C | 21.6 °C | 18.3 °C | 13.2 °C | 8.4 °C |
- Very cold 10 °C or less
- Cold 10 to 15 °C
- Cool 15 to 20 °C
- Comfortable 20 to 25 °C
- Warm 25 to 28 °C
- Very warm over 28 °C
The words describe how the water feels to swim in. They are ours, not an official standard.
Air quality
Averaged over a shorter period (2022–2025) than the twenty-year averages above, and not counted towards good or best months.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Air pollution (PM2.5) 2022–2025 | 10 µg/m³ | 10.9 µg/m³ | 9.6 µg/m³ | 11.5 µg/m³ | 11.9 µg/m³ | 16.7 µg/m³ | 14.1 µg/m³ | 12.4 µg/m³ | 9 µg/m³ | 8.9 µg/m³ | 8.1 µg/m³ | 8.6 µg/m³ |
| Air pollution (PM2.5, daily peak) 2022–2025 | 18.4 µg/m³ | 19.1 µg/m³ | 16.6 µg/m³ | 18.8 µg/m³ | 20.2 µg/m³ | 26.9 µg/m³ | 20.8 µg/m³ | 19.7 µg/m³ | 14.3 µg/m³ | 15 µg/m³ | 14.9 µg/m³ | 14.8 µg/m³ |
- Good 15 µg/m³ or less
- Fair 15 to 25 µg/m³
- Moderate 25 to 37.5 µg/m³
- Poor 37.5 to 50 µg/m³
- Very poor 50 to 75 µg/m³
- Extremely poor over 75 µg/m³
Each figure is compared with the World Health Organization's guideline for a day's air, 15 µg/m³ or less, and with its interim targets above that. The words are ours: the WHO does not name its steps. The figures are modelled monthly averages, so single days can be well above them. The daily peak is the average of each day's highest hour, shaded on the same scale.