Ontario Intl climate by month
Averages and records for each calendar month at Ontario Intl, United States, from 1998 to 2026. The warmest month is August, averaging 34.7°C; the coolest is December at 19.2°C.
| Month | Avg high | Avg low | Record high | Record low | Years |
|---|---|---|---|---|---|
| January | 19.7°C | 6.7°C | 32.2°C31 January 2003 | −3.8°C14 January 2007 | 28 / 28 |
| February | 19.8°C | 7.2°C | 32.8°C27 February 2026 | −1.6°C20 February 2018 | 28 / 28 |
| March | 21.8°C | 9.0°C | 37.8°C19 March 2026 | 0.6°C12 March 2006 | 28 / 28 |
| April | 23.9°C | 10.6°C | 38.3°C26 April 2004 | 0.6°C10 April 1999 | 28 / 28 |
| May | 26.3°C | 13.1°C | 39.4°C28 May 2003 | 5.6°C1 May 1999 | 28 / 29 |
| June | 30.2°C | 15.6°C | 44.4°C20 June 2016 | 7.8°C5 June 1999 | 29 / 29 |
| July | 34.1°C | 18.3°C | 47.2°C6 July 2018 | 13.3°C12 July 2001 | 29 / 29 |
| August | 34.7°C | 18.8°C | 44.4°C31 August 2017 | 13.3°C8 August 1999 | 29 / 29 |
| September | 32.6°C | 17.4°C | 47.8°C5 September 2020 | 10.6°C27 September 2013 | 28 / 29 |
| October | 27.9°C | 13.8°C | 41.7°C1 October 2012 | 5.0°C31 October 2019 | 28 / 28 |
| November | 23.3°C | 9.3°C | 36.7°C3 November 2010 | 0.0°C30 November 2004 | 28 / 28 |
| December | 19.2°C | 6.5°C | 30.6°C1 December 2021 | −2.2°C22 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 28 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.