Weather in San Juan in September 2025
- September is usually the hottest month of the year in San Juan;
Average weather
Average temperature in San Juan in September
The temperature in September is +32°C on average, with a range between a maximum of +35°C during the day and a minimum of +24°C at night.
The average maximum temperature goes down 9% by the end of the month, compared with the beginning of the month, from +32°C to +31°C.
Is San Juan warm or cold in September?
San Juan is typically hot in September.
Maximum temperatures go up compared to the previous month from +31°C to +31°C. The minimum temperature also goes up from +26°C to +26°C.
Make sure that you pack your summer linen and swimming costumes; it’s probably going to be hot.
September is the hottest month in San Juan, here is the comparison with other months:
Water temperature in San Juan in September
Water in San Juan in September is Very warm. It varies from +29°C to +30°C, with an average of +29°C. This is almost similar to the air temperature, which averages +31°C.
The water temperature in September is one of the warmest of the entire year:
Can you swim in San Juan in September?
Climate in San Juan in September
| August | September | October | ||||
|---|---|---|---|---|---|---|
| Avg. temperature | ||||||
| +31°C | +31°C | +30°C | ||||
| Min. temperature | ||||||
| +23°C | +23°C | +23°C | ||||
| Max. temperature | ||||||
| +35°C | +35°C | +36°C | ||||
| Rainfall | ||||||
| 106 mm | 148 mm | 151 mm | ||||
| Wind | ||||||
| 3 m/s | 2 m/s | 2 m/s | ||||
| Avg. water temperature | ||||||
| +29°C | +29°C | +29°C | ||||
| Humidity | ||||||
| 78% | 78% | 78% | ||||
| Air pressure | ||||||
| 1015 HPa | 1013 HPa | 1012 HPa | ||||
| Sunny days | ||||||
| 1 | 1 | 1 | ||||
| Cloudy days | ||||||
| 3 | 2 | 3 | ||||
| Rainy days | ||||||
| 22 | 20 | 21 | ||||
| Snowy days | ||||||
| 0 | 0 | 0 | ||||
September weather is still as ok as in August. The temperature levels stay the same in the area of +31°C for average maximum temperature during the day. Prepare for more rain. Average rainfall goes from 106 mm to 148 mm. Humidity levels don’t change as the month goes on, averaging around 78%. Winds are calmer in comparison to August, going down from 3 m/s to 2 m/s on average. The amount of sunny days stay about the same, averaging 1 sunny days during the month.
October brings much the same weather, it remains ok.
Wind
The average wind speed is 3 m/s getting up to 4 m/s which is a light breeze; barely moving the tree leaves.
The average wind speed in San Juan is gradually increasing during September, going from 4 m/s to 4 m/s over the course of the month.
Rain
How was the weather last September in San Juan?
Climate Change over Years
The climate in San Juan in September has not changed much over the last 43 years.
The average temperature was the lowest in 2008 (+29°C) and the highest in 2013 (+31°C). The driest year was 1994 with only 675 mm of rainfall, and the wettest year was 2023 with 2338 mm.
FAQ
Is September a good time to visit San Juan?
Can you sunbathe in San Juan in September?
Can you swim in San Juan in September?
Is San Juan rainy in September?
Is it sunny in San Juan in September?
Monthly weather in San Juan
Source of the data
For this page, we’ve looked at the typical weather in San Juan, based on historical hourly weather data from January 1, 1979, to December 31, 2023.
For past dates, we show actual recorded data at the location at that time. Forecasts are based on recorded weather during that day of the year, averaged over the total years for which we have records (unless stated otherwise). The daily temperature is the highest recorded temperature in the shadow during that day.