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San Sebastian Weather in September
September in San Sebastian brings very high temperatures, with daytime highs of 31°C (88°F) and nights around 25°C (77°F). It's also the wettest month of the year, so an umbrella is a must.
Rainfall in San Sebastian in September
With the year's heaviest rain occurring this month, it's best to be equipped with a poncho to handle the frequent downpours. You can typically expect 17 days of rain this month, averaging around 158 mm (6.2 in). Wet weather is a regular and significant part of this month. Frequent days of rain combined with high totals means proper waterproofs are worth packing.
Temperature in San Sebastian in September
September in San Sebastian brings very high temperatures, with highs of 31°C (88°F) and nights around 25°C (77°F). Indoor breaks or shaded spots can make the warmer part of the day much more comfortable. With overnight lows of 25°C (77°F), evenings and nights remain warm. Light clothing and an open window or fan can help you sleep comfortably.If you're looking for dry conditions and comfortable temperatures, September may not be the ideal month to visit San Sebastian. Our weather planner can help you explore destinations with more pleasant weather conditions.
San Sebastian Temperature in September
Min Temperature
25°C (77°F)
Max Temperature
31°C (88°F)
Chance of Rain
57%
Precipitation
158 mm (6.2 in)
Rainy days
17 days
San Sebastian Weather by Month
Pick a month to see the average temperature, rainfall and sunshine in San Sebastian - and find the best time to visit.
Daily Historical Temperatures
48-year average (1977-2025)
Based on our historical records, temperatures in San Sebastian typically stay consistent throughout September, with daily highs averaging around 31°C (88°F). Nights are warm, with lows around 24°C (75°F).
Average temperatures in September
Historical weather records for San Sebastian in September
Browse day-by-day weather records for San Sebastian spanning 51 years. Select any month and year to see actual temperatures, rainfall, and conditions recorded on each day.
San Sebastian historical weather extremes in September
According to our 26 years of weather records for San Sebastian, the following extremes were recorded between 1999 and 2025.
- On September 26, 2012, temperatures climbed to 36°C (97°F), marking the warmest September day on record.
- On September 18, 2022, San Sebastian saw its coldest September day with temperatures maxing out at 26°C (79°F).
- The coldest night in September in San Sebastian was on September 30, 2014, 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 →
perfect weather
pleasant
tolerable
unpleasant
poor
Perfect weather is subjective. On this map perfect weather has been defined with temperatures between 20°C (68°F) and 29°C (84°F) and not too much precipitation (less than 90 mm (3.5 in) a month).
What to Wear in San Sebastian in September
Warm temperatures in September make for comfortable sightseeing weather. Pack breathable fabrics like cotton shirts, knee-length shorts or skirts, and comfortable walking shoes. A thin long sleeve for indoor spaces is handy. Heavy rain is guaranteed, please bring a good poncho and waterproof everything!
What To Do in San Sebastian in September
We rated the following activities from 1 (least suitable) to 10 (best) to do.
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Cycling7/10 -
Walking7/10 -
Camping6/10 -
Outdoor sports7/10
San Sebastian 3-Day Forecast
More climate data for San Sebastian
See the full San Sebastian climate overview or explore weather in Puerto Rico.
Popular in September
Where to go in September - average daytime high across popular destinations.
San Juan
31°C (88°F) Fajardo30°C (86°F) Luquillo30°C (86°F) Aguada
30°C (86°F) Rincon
30°C (86°F) Rio Grande31°C (88°F) Culebra30°C (86°F) Vieques30°C (86°F) Bucket list
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