Rio Grande Weather in September
In Rio Grande, September brings very high daytime temperatures around 31°C (88°F), with nights cooling to 26°C (79°F). It is the wettest month of the year, so expect more rainfall than usual.
Rainfall in Rio Grande in September
Experience the peak rainfall in this month, with heavy showers being the norm. A poncho is essential to stay dry and comfortable. Records from the past 30 years suggest around 18 days of rain, with 164 mm (6.5 in) average for the month. This is a wet month with frequent and often heavy showers. Both the number of rain days and the total rainfall are high.
Temperature in Rio Grande in September
Daytime highs in Rio Grande in September reach 31°C (88°F), with nights around 26°C (79°F). For most visitors, the main thing to prepare for is the heat during the day. With overnight lows of 26°C (79°F), evenings and nights remain warm. Light clothing and an open window or fan can help you sleep comfortably.
Sunshine in Rio Grande in September
Enjoy a sunny month with about 236 hours of sunshine, the clear skies make Rio Grande even more beautiful.
Wind Speed in Rio Grande in September
Wind speeds average 3 m/s (6 knots) during September. At this speed, light breezes keep leaves and small twigs in gentle motion while the wind also provides natural cooling. Since this is an average, some days are more tranquil while others have more persistent light winds that are more noticeable.
Average water temperature in September
With water at 29°C (84°F), conditions are warm and calm. Perfect for those who like tropical water temperatures, though it won't cool you down much.September in Rio Grande 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 Rio Grande's climate page.
Rio Grande Temperature in September
Min Temperature
26°C (79°F)
Max Temperature
31°C (88°F)
Water Temperature
29°C (84°F) *
Chance of Rain
60%
Precipitation
164 mm (6.5 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 Rio Grande 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 Rio Grande in September
Browse day-by-day weather records for Rio Grande spanning 51 years. Select any month and year to see actual temperatures, rainfall, and conditions recorded on each day.
Rio Grande historical weather extremes in September
Based on 49 years of weather observations in Rio Grande between 1976 and 2025, these are the recorded extremes.
- The hottest September day on record in Rio Grande reached 35°C (95°F) (September 18, 1995).
- Rio Grande experienced its chilliest September day on September 13, 1985, reaching only 25°C (77°F).
- The lowest overnight temperature recorded in September was 22°C (72°F) (September 9, 1988).
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 →
perfect weather
pleasant
tolerable
unpleasant
poor
What to Wear in Rio Grande in September
Warm weather calls for comfortable, breathable clothing in September. Cotton t-shirts, shorts, light dresses, and sandals are perfect. You might still want a light layer for evenings or air-conditioned places (for example buses). Also bring a poncho, it will rain a lot! Waterproof everything you can. With water temperatures around 29°C (84°F), swimming conditions are excellent. Pack your swimsuit, goggles, and maybe some water shoes. And with plenty of sunshine hours, don’t forget sunglasses, sunscreen, and maybe a sun hat.What To Do in Rio Grande 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 Rio Grande's climate page.
Temperature Rainfall Sunshine Humidity Wind Speed Water Temp
See the full Rio Grande climate overview or explore weather in Puerto Rico.
