San Juan weather in January
In January, San Juan has daytime highs averaging 28 °C, nights around 21 °C, with 10 wet days, and a sea temperature of 27 °C. Figures are 1991–2020 climate normals.
- 27.9°C Average high
- 21.5°C Average low
- 10days Wet days
- 43mm Rainfall
- 26.5°C Sea temperature
- 11h Daylight
Daily temperatures through January
How January 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 January | 28.0 °C | 21.8 °C | 34 % |
| 11–20 January | 27.8 °C | 21.4 °C | 36 % |
| 21–31 January | 28.0 °C | 21.2 °C | 32 % |
What to expect
| Measure | Typical January | Share of the month |
|---|---|---|
| Days above 25 °C | 31 of 31 | 98 % |
| Days above 30 °C | 1.6 of 31 | 5 % |
| Days below 0 °C | 0 of 31 | 0 % |
| Days with more than 1 mm rain | 10 of 31 | 34 % |
Conditions in January
| Measure | Average |
|---|---|
| Mean temperature | 24 °C |
| Record high (1991–2020) | 32 °C |
| Record low (1991–2020) | 17 °C |
| Relative humidity | 80 % |
| Wind speed | 20 km/h |
| Cloud cover | 38 % |
Where San Juan ranks in January
| Ranking | Position | Value |
|---|---|---|
| The warmest places in North America in January | 30thof 50 | 28 °C |
January compared with the months around it
| Month | Avg high | Rainfall | Cloud |
|---|---|---|---|
| January | 27.9 °C | 43 mm | 38 % |
| February | 28.5 °C | 31 mm | 36 % |
| March | 29.3 °C | 41 mm | 39 % |
| November | 28.9 °C | 105 mm | 52 % |
| December | 28.1 °C | 49 mm | 41 % |
See all twelve months for San Juan
- January is the 12th warmest month here.
- It is the 3rd driest month of the year.
- It ranks 2nd for least cloud cover.
- Days last about 11 hours from sunrise to sunset.
- It rains on 10 of 31 days — 34 % of the month.
- Nights are about 6.4 °C cooler than the middle of the day.
- The hottest January day on record since 1991 reached 32 °C, 3.7 °C above the usual daytime high.
- Beach score: 84 / 100 — see how this is calculated.
Nearby destinations in January
| Destination | Avg high | Wet days | Sea |
|---|---|---|---|
| San Juan | 28 °C | 10 | 27 |
| Carolina | 28 °C | 15 | 27 |
| Charlotte Amalie | 26 °C | 9 | 26 |
| Road Town | 26 °C | 8 | 26 |
| La Romana | 28 °C | 4 | 27 |
| San Pedro de Macorís | 28 °C | 4 | 27 |
| Gustavia | 26 °C | 8 | 27 |
| Basseterre | 26 °C | 10 | 27 |
| Santo Domingo | 28 °C | 11 | 27 |
QuestionsJanuary in San Juan, answered
How warm is San Juan in January?
Daily highs average 28 °C and nights fall to about 21 °C, a spread of 6.4 °C between afternoon and dawn. That makes January the 12th warmest month of the year here.
Does it rain much in San Juan in January?
January averages 43 mm of rain, spread over about 10 of the 31 days — 34 % of the month. Cloud cover averages 38 % of the sky.
Is the sea warm enough to swim in January?
The sea averages 27 °C off San Juan in January. 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 January?
San Juan averages 11 hours between sunrise and sunset in January. 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.