Riverside weather in December
In December, Riverside has daytime highs averaging 18 °C, nights around 5.0 °C, with 5.8 wet days. Figures are 1991–2020 climate normals.
- 17.7°C Average high
- 5.0°C Average low
- 5.8days Wet days
- 67mm Rainfall
- 9.9h Daylight
Daily temperatures through December
How December develops
Averages for the first, middle and last part of the month, from daily 1991–2020 normals. Chance of rain is the share of years in which that calendar day recorded more than 1 mm.
| Days | Avg high | Avg low | Chance of rain |
|---|---|---|---|
| 1–10 December | 18.8 °C | 6.0 °C | 17 % |
| 11–20 December | 17.5 °C | 5.2 °C | 21 % |
| 21–31 December | 17.1 °C | 4.0 °C | 18 % |
- Average highs fall from 18.8 °C early in December to 17.1 °C by the end of it.
What to expect
| Measure | Typical December | Share of the month |
|---|---|---|
| Days above 25 °C | 1.2 of 31 | 4 % |
| Days above 30 °C | 0 of 31 | 0 % |
| Days below 0 °C | 2.6 of 31 | 8 % |
| Days with more than 1 mm rain | 5.8 of 31 | 19 % |
Conditions in December
| Measure | Average |
|---|---|
| Mean temperature | 10 °C |
| Record high (1991–2020) | 29 °C |
| Record low (1991–2020) | -3.4 °C |
| Relative humidity | 62 % |
| Wind speed | 9.8 km/h |
| Cloud cover | 44 % |
December compared with the months around it
| Month | Avg high | Rainfall | Cloud |
|---|---|---|---|
| January | 18.1 °C | 92 mm | 49 % |
| February | 18.7 °C | 108 mm | 51 % |
| October | 27.6 °C | 22 mm | 27 % |
| November | 22.3 °C | 29 mm | 36 % |
| December | 17.7 °C | 67 mm | 44 % |
See all twelve months for Riverside
- December is the 12th warmest month here.
- It is the 10th driest month of the year.
- It ranks 9th for least cloud cover.
- Days last about 9.9 hours from sunrise to sunset.
- It rains on 5.8 of 31 days — 19 % of the month.
- Nights are about 13 °C cooler than the middle of the day.
- The hottest December day on record since 1991 reached 29 °C, 11 °C above the usual daytime high.
QuestionsDecember in Riverside, answered
How warm is Riverside in December?
Daily highs average 18 °C and nights fall to about 5.0 °C, a spread of 13 °C between afternoon and dawn. That makes December the 12th warmest month of the year here.
Does it rain much in Riverside in December?
December averages 67 mm of rain, spread over about 6 of the 31 days — 19 % of the month. Cloud cover averages 44 % of the sky.
How long are the days in December?
Riverside averages 9.9 hours between sunrise and sunset in December. Day length is computed from latitude and date, so it is exact rather than modelled — but it says nothing about how much of that time is sunny.
Data sources and method
- ERA5 / ERA5-Land reanalysis — Copernicus Climate Change Service (C3S), ECMWF. Copernicus Licence
- Open-Meteo — Open-Meteo.com. CC BY 4.0
- NOAA OISST v2.1 — NOAA Physical Sciences Laboratory. Public domain
- GeoNames — GeoNames.org. CC BY 4.0
- Normal period
- 1991–2020
- Dataset version
- era5-1991-2020-scores1.1
- Last processed
Measured values come from ERA5 reanalysis and are reproduced unchanged. Calculated by us: daylight hours, beach and comfort scores, monthly rankings, threshold day counts, chance of a wet day by date, ten-day averages within the month. Full formulas are on the methodology page.
Contains modified Copernicus Climate Change Service information 2026. Neither the European Commission nor ECMWF is responsible for any use that may be made of the Copernicus information or data it contains.