Brentwood weather by month
Measured at Islip/Macarthur Arpt
Averages and records for each calendar month at Islip/Macarthur Arpt, United States, from 1963 to 2026. The warmest month is July, averaging 27.9°C; the coolest is January at 3.6°C.
| Month | Avg high | Avg low | Record high | Record low | Years |
|---|---|---|---|---|---|
| January | 3.6°C | −4.8°C | 20.6°C29 January 2002 | −22.2°C18 January 1965 | 63 / 63 |
| February | 4.6°C | −4.1°C | 21.7°C16 February 2023 | −25.6°C13 February 1967 | 63 / 63 |
| March | 8.8°C | −0.2°C | 27.8°C13 March 1990 | −17.8°C18 March 1967 | 63 / 63 |
| April | 14.5°C | 4.7°C | 34.4°C17 April 2002 | −8.9°C1 April 1969 | 63 / 63 |
| May | 20.0°C | 10.2°C | 36.7°C20 May 1996 | 0.0°C1 May 2008 | 63 / 63 |
| June | 24.9°C | 15.6°C | 38.3°C24 June 2025 | 5.6°C1 June 1967 | 63 / 63 |
| July | 27.9°C | 19.2°C | 40.0°C3 July 1966 | 9.4°C2 July 1965 | 63 / 63 |
| August | 27.3°C | 18.6°C | 37.8°C2 August 1975 | 7.2°C31 August 1965 | 63 / 63 |
| September | 23.5°C | 14.4°C | 34.4°C3 September 1973 | 3.3°C24 September 1963 | 63 / 64 |
| October | 17.9°C | 8.1°C | 31.7°C2 October 2019 | −5.0°C31 October 1966 | 63 / 63 |
| November | 12.2°C | 3.0°C | 26.7°C7 November 2022 | −11.7°C24 November 1989 | 63 / 63 |
| December | 6.5°C | −1.8°C | 25.0°C7 December 1998 | −18.3°C31 December 1963 | 63 / 63 |
Years shows the number behind the average high, then the number holding a record for that month. They differ because a year contributes an average only when the month has at least 25 days of readings, while a single reading is enough to set a record. The average low is withheld on the same 25-day rule and is counted separately again; it is shown as a dash where the archive cannot support it. Across the twelve months here the averages rest on 63 to 63 years each.
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Climate at nearby stations
The closest stations with twelve months of archive of their own, nearest first.
Every figure on this page is computed from NOAA GHCN-Daily observations stored per station, per year, per month. Nothing is modelled, interpolated or estimated, and a month the archive never covered is left out rather than filled in. A station appears here only once all twelve months carry an average from at least 10 years. See how this is built.