San Juan Weather in September
In San Juan, September brings very high daytime temperatures around 31°C (88°F), with nights cooling to 25°C (77°F). It is the wettest month of the year, so expect more rainfall than usual.
Rainfall in San Juan in September
This month is known for its intense rain, often falling heavily. Having a poncho will help you stay dry during the showers. Past climate data indicates that roughly 18 days will see rain, totalling around 159 mm (6.3 in) for the month. Rain falls regularly this month and can be quite heavy when it does. Showers can be substantial, so waterproof gear is a good idea.
Temperature in San Juan in September
In September, expect very high temperatures in San Juan, with highs of 31°C (88°F) and lows of 25°C (77°F) at night. If you're spending a lot of time outdoors, it helps to plan around the warmer part of the day. Nights are warm at 25°C (77°F). It's worth making sure your accommodation has decent ventilation or air conditioning.
Sunshine in San Juan in September
The city usually sees around 236 hours of sunlight, indicating many sunny days — a great month for sightseeing.
Wind Speed in San Juan in September
Average wind speeds reach 3 m/s (6 knots) in September, creating light breezes that feel pleasant throughout the day. Some days are calmer, while others bring slightly more active breezes.
Average water temperature in September
The water is 29°C (84°F) — very warm by most standards. Comfortable to swim in, but not particularly refreshing if you're looking to cool off.September in San Juan can still be great, but if you prefer pleasant temperatures along with dry and sunny conditions, our weather planner can help you explore other options in the world.
Check the conditions for any month of the year.
For a detailed overview over the year and the best time to visit Puerto Rico, check out our San Juan's climate page.
San Juan Temperature in September
Min Temperature
25°C (77°F)
Max Temperature
31°C (88°F)
Water Temperature
29°C (84°F)
Chance of Rain
60%
Precipitation
159 mm (6.3 in)
Rainy days
18 days
Humidity
76%
Windspeed
3 m/s (6 knots)
Sunshine
236 hours
Percentage Sunshine
64%
Daily Historical Temperatures
50-year average (1976-2025)
Based on our historical records, temperatures in San Juan typically stay consistent throughout September, with daily highs averaging around 31°C (88°F). Nights are warm, with lows around 26°C (79°F).
Average temperatures in September
Daily Historical Precipitation
50-year average (1976-2025)
Average daily rainfall for each day of the month based on long-term records.
Average precipitation in September
Historical weather for San Juan in September
Browse day-by-day weather records for San Juan spanning 51 years. Select any month and year to see actual temperatures, rainfall, and conditions recorded on each day.
San Juan historical weather extremes in September
Based on 49 years of weather observations (1976-2025), these are the most extreme conditions recorded in San Juan.
- The warmest day in September was on September 29, 2011, with a maximum of 36°C (97°F).
- The coldest September day was on September 13, 1985, with a maximum of 24°C (75°F).
- The coldest night in September in San Juan was on September 9, 1988, with a minimum of 21°C (70°F).
Best Places in Puerto Rico in September
Find out more about the weather in Puerto Rico and which places have the best travel conditions in this month. See all of Puerto Rico in September →
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What to Wear in San Juan in September
Warm but pleasant conditions in San Juan in September. Focus on lightweight, maybe with natural fabrics, cotton blend shirts, comfortable shorts, and breathable footwear. A light cover-up for sun protection is smart too. It's going to pour! Pack a good poncho and prepare for very wet conditions. Expect water temperatures of around 29°C (84°F), which is ideal for taking a refreshing dip. Bring swimwear and consider packing a towel for drying off. Don't forget sun protection, sunglasses, sunscreen, and a hat. These are all good ideas with this much sunshine.What To Do in San Juan in September
We rated the following activities from 1 (least suitable) to 10 (best) to do.
Check the conditions for any month of the year.
For a detailed overview over the year and the best time to visit Puerto Rico, check out our San Juan's climate page.
Temperature Rainfall Sunshine Humidity Wind Speed Water Temp
See the full San Juan climate overview or explore weather in Puerto Rico.
