Eureka climate by month
Averages and records for each calendar month at Eureka, United States, from 1941 to 2026. The warmest month is September, averaging 17.4°C; the coolest is January at 12.6°C.
| Month | Avg high | Avg low | Record high | Record low | Years |
|---|---|---|---|---|---|
| January | 12.6°C | 5.1°C | 25.6°C12 January 1986 | −3.9°C13 January 2007 | 85 / 85 |
| February | 12.9°C | 5.6°C | 26.7°C7 February 1987 | −2.8°C1 February 1950 | 85 / 85 |
| March | 13.0°C | 6.0°C | 24.4°C31 March 1987 | −1.1°C10 March 1951 | 85 / 85 |
| April | 13.6°C | 7.0°C | 26.7°C9 April 1989 | 0.0°C1 April 1999 | 85 / 85 |
| May | 14.8°C | 8.8°C | 28.3°C16 May 2008 | 1.7°C8 May 2002 | 85 / 85 |
| June | 16.1°C | 10.3°C | 29.4°C17 June 1945 | 4.4°C8 June 1999 | 85 / 85 |
| July | 16.8°C | 11.4°C | 25.0°C28 July 2015 | 7.2°C3 July 2018 | 85 / 85 |
| August | 17.3°C | 11.8°C | 27.8°C30 August 1968 | 7.2°C31 August 1999 | 85 / 85 |
| September | 17.4°C | 10.7°C | 30.6°C2 September 2017 | 5.0°C30 September 1946 | 84 / 85 |
| October | 16.2°C | 8.9°C | 30.6°C26 October 1993 | 0.0°C29 October 1971 | 84 / 84 |
| November | 14.5°C | 6.9°C | 25.6°C19 November 1987 | −1.7°C19 November 1994 | 84 / 84 |
| December | 12.8°C | 5.3°C | 25.0°C30 December 1963 | −6.1°C9 December 1972 | 85 / 85 |
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 84 to 85 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.