Fullerton Muni climate by month
Averages and records for each calendar month at Fullerton Muni, United States, from 1998 to 2026. The warmest month is August, averaging 30.6°C; the coolest is December at 20.3°C.
| Month | Avg high | Avg low | Record high | Record low | Years |
|---|---|---|---|---|---|
| January | 20.9°C | 8.0°C | 34.4°C31 January 2003 | −2.1°C14 January 2007 | 28 / 28 |
| February | 20.9°C | 8.7°C | 34.4°C15 February 2016 | 1.7°C2 February 2002 | 27 / 28 |
| March | 22.1°C | 10.6°C | 37.8°C17 March 2026 | 2.2°C12 March 2006 | 27 / 28 |
| April | 23.2°C | 12.1°C | 38.9°C27 April 2004 | 3.9°C10 April 1999 | 29 / 29 |
| May | 24.3°C | 14.7°C | 40.0°C2 May 2004 | 7.8°C1 May 1999 | 28 / 28 |
| June | 26.4°C | 16.8°C | 42.8°C20 June 2016 | 11.1°C5 June 1999 | 28 / 28 |
| July | 29.4°C | 18.8°C | 46.7°C6 July 2018 | 14.4°C24 July 1999 | 29 / 29 |
| August | 30.6°C | 19.1°C | 41.7°C27 August 2009 | 13.3°C12 August 2010 | 29 / 29 |
| September | 29.8°C | 18.0°C | 45.0°C6 September 2024 | 12.2°C28 September 2013 | 28 / 29 |
| October | 27.0°C | 14.7°C | 41.7°C23 October 2017 | 7.2°C29 October 2009 | 28 / 28 |
| November | 23.7°C | 10.5°C | 37.2°C3 November 2010 | 1.1°C29 November 2010 | 28 / 28 |
| December | 20.3°C | 7.8°C | 30.6°C12 December 2010 | −0.6°C24 December 1998 | 28 / 28 |
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 27 to 29 years each.
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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.