Oceanside weather in December
In December, Oceanside has daytime highs averaging 17 °C, nights around 8.8 °C, with 5.5 wet days, and a sea temperature of 16 °C. Figures are 1991–2020 climate normals.
- 17.1°C Average high
- 8.8°C Average low
- 5.5days Wet days
- 56mm Rainfall
- 16.0°C Sea temperature
- 10.0h 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 | 17.8 °C | 9.7 °C | 15 % |
| 11–20 December | 17.0 °C | 9.0 °C | 20 % |
| 21–31 December | 16.6 °C | 7.9 °C | 18 % |
- Average highs fall from 17.8 °C early in December to 16.6 °C by the end of it.
What to expect
| Measure | Typical December | Share of the month |
|---|---|---|
| Days above 25 °C | 0.03 of 31 | 0 % |
| Days above 30 °C | 0 of 31 | 0 % |
| Days below 0 °C | 0 of 31 | 0 % |
| Days with more than 1 mm rain | 5.5 of 31 | 18 % |
Conditions in December
| Measure | Average |
|---|---|
| Mean temperature | 13 °C |
| Record high (1991–2020) | 26 °C |
| Record low (1991–2020) | 1.6 °C |
| Relative humidity | 75 % |
| Wind speed | 12 km/h |
| Cloud cover | 44 % |
December compared with the months around it
| Month | Avg high | Rainfall | Cloud |
|---|---|---|---|
| January | 17.2 °C | 73 mm | 47 % |
| February | 17.0 °C | 91 mm | 50 % |
| October | 22.9 °C | 18 mm | 36 % |
| November | 20.0 °C | 26 mm | 38 % |
| December | 17.1 °C | 56 mm | 44 % |
See all twelve months for Oceanside
- December is the 11th warmest month here.
- It is the 9th driest month of the year.
- It ranks 7th for least cloud cover.
- Days last about 10.0 hours from sunrise to sunset.
- It rains on 5.5 of 31 days — 18 % of the month.
- Nights are about 8.3 °C cooler than the middle of the day.
- The hottest December day on record since 1991 reached 26 °C, 8.9 °C above the usual daytime high.
- Beach score: 38 / 100 — see how this is calculated.
QuestionsDecember in Oceanside, answered
How warm is Oceanside in December?
Daily highs average 17 °C and nights fall to about 8.8 °C, a spread of 8.3 °C between afternoon and dawn. That makes December the 11th warmest month of the year here.
Does it rain much in Oceanside in December?
December averages 56 mm of rain, spread over about 5 of the 31 days — 18 % of the month. Cloud cover averages 44 % of the sky.
Is the sea warm enough to swim in December?
The sea averages 16 °C off Oceanside in December. Most people find water below 20 °C bracing and above 25 °C comfortable for a long swim; this figure is a monthly surface average, so a sheltered bay on a still afternoon can be warmer.
How long are the days in December?
Oceanside averages 10.0 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.