Climate Overview
The climate in San Juan is warm and mild. The average annual temperature is 25°C and approximately 538mm of precipitation falls per year. September is the wettest month, receiving around 81mm of rainfall. San Juan is in the Northern Hemisphere. Summer begins at the end of June and lasts through September. The summer months are: August, July, June. The coldest months are January, December, February, when temperatures can drop to 12°C.
Temperature
Temperatures in San Juan vary considerably across the year, with a 25°C difference between the coldest and warmest months. August is the hottest month, with daytime highs reaching 37°C and an average of 31°C. January is the coolest month, with minimum temperatures around 12°C and an average of 16°C. On average, daily temperatures fluctuate by about 11°C between overnight lows and afternoon highs. The sharpest temperature change occurs between October and November, with a 4°C shift in average temperatures.
Precipitation
San Juan is a relatively dry area, receiving approximately 538mm of precipitation annually, which averages out to around 45mm per month. The wettest month is September, averaging 81mm of rainfall. July and May also tend to see above-average precipitation. The driest month is February, with just 18mm. That's 62mm less than September, the wettest month. Precipitation varies noticeably between seasons, with the second half (July to December) of the year generally seeing more rainfall.
Wind
San Juan is mildly breezy, with an average annual wind speed of 16km/h. For context, sustained winds below 12km/h are generally light, while anything above 25km/h is considered strong. The windiest month is April, averaging 19km/h, though still comfortable for most outdoor activities. The calmest conditions occur in September, with average winds dropping to 13km/h, making it an ideal period for wind-sensitive activities. There is moderate seasonal variation in wind speed, with a 6km/h gap between the calmest and windiest months. Wind tends to pick up during the summer months. The seasonal averages are 16km/h in winter, 19km/h in spring, 18km/h in summer, 14km/h in autumn.
Seasons
8 days until Autumn
It is currently summer in San Juan, which began on June 21, 2026. San Juan is in the Northern Hemisphere, where spring begins in March, summer in June, autumn in September, and winter in December. The warmest period peaks in August at around 37°C, while the coldest stretch bottoms out in January near 12°C. Autumn is next, beginning on September 23, 2026 (8 days from now).
Spring
Temperatures range from 18 to 34°C. Rainfall is relatively light, with around 141mm over the season and a monthly average of 47mm. Winds are moderate at around 19km/h. Light layers work well as temperatures warm through the season. It is a great time to be outdoors.
Summer
Temperatures range from 25 to 37°C. Precipitation is moderate at around 175mm for the season, averaging 58mm per month. Winds are moderate at around 18km/h. Stay hydrated, wear sun protection, and seek shade during the hottest hours of the day.
Autumn
Temperatures range from 17 to 35°C. Precipitation is moderate at around 158mm for the season, averaging 53mm per month. Winds are generally light, averaging 14km/h. Layered clothing works best as temperatures gradually cool. Enjoy the crisp air and changing scenery.
Winter
Temperatures range from 12 to 26°C. Rainfall is relatively light, with around 64mm over the season and a monthly average of 21mm. Winds are moderate at around 16km/h. A light jacket or sweater is usually sufficient, though cooler evenings may call for an extra layer.
Best Time to Visit
The best time to visit San Juan is during January, February, March, November and December, when the weather is most comfortable for travellers. During these months, average temperatures hover around 19°C with modest rainfall averaging 28mm per month. By contrast, August can be uncomfortably hot with temperatures reaching 37°C. With minimal rainfall expected, you can pack light and plan outdoor activities with confidence.
Monthly Climate Data
The table below shows monthly climate averages for San Juan based on historical weather data. Min and max temperatures represent typical overnight lows and afternoon highs for each month, shown in degrees Celsius (°C). Precipitation is measured in millimetres (mm) and indicates the average total rainfall per month. Wind speed is the average sustained speed in kilometres per hour (km/h). All values are based on averages from over 10 years of historical weather data. The current month is highlighted for quick reference.
