San Juan in September
In September, San Juan averages 31°C (88°F) during the day and 25°C (77°F) at night, with frequent rain — about 15 days of the month see precipitation (145 mm total).
Off-peakConditions are warm and beach-friendly. Plan for unsettled weather and bring rain gear.
It's peak hurricane season in San Juan during September. Travel is possible but expect storm risk, possible flight disruption, and generally lower travel insurance coverage.
How September compares to the rest of the year in San Juan
September is in the middle of the year for warmth in San Juan (4th of 12) and one of the wettest months (3rd of 12). Daytime temperature runs 1°C above the annual average (30°C). September runs 1°C cooler than August (32°C) and stays flat into October.
September sunrise & sunset in San Juan
Times shown for San Juan local time (America/Puerto_Rico), calculated for the 15th of September. They shift by a few minutes day to day across the month.
Photography light in San Juan — September
Golden-hour and blue-hour windows for the 15th of September, in San Juan's local time. Use these for soft warm light (golden) or cool architectural twilight (blue).
📅 When to book — San Juan in September
Travel writers usually only tell you when to go. Here's when to book flights and lodging for the best mix of price and availability, based on September's tier (Off-peak) and San Juan's popularity.
Crowds & pricing — September in San Juan
This is off-peak for San Juan — the lowest prices of the year and the fewest crowds, but with real trade-offs: some restaurants, hotels, and beach businesses may close for the season; weather conditions can make outdoor activities unpredictable; and a handful of seasonal sights run reduced hours or close entirely. Great if you prefer a quiet local rhythm and don't mind the climate giving you reasons to choose indoor activities.
Why this tier: peak hazard season (1 active)
Sun & mosquito risk — September in San Juan
UV is a clear-sky sea-level estimate — clouds, altitude, and reflective surfaces (snow, water) shift it ±30%. Mosquito risk is climate-derived only; for current disease advisories (dengue, malaria, zika) check the CDC or WHO travel pages before your trip.
Sea temperature in San Juan — September
Across the year San Juan's sea swings from 26.5°C (February) to 30.4°C (October) — September sits at 30.2°C.
San Juan in other months
| Month | Avg high | Avg low | Rainfall | Rain days | Snow days |
|---|---|---|---|---|---|
| January | 28°C / 82°F | 21°C / 70°F | 75 mm | 11 | — |
| February | 28°C / 82°F | 21°C / 70°F | 55 mm | 9 | — |
| March | 29°C / 84°F | 22°C / 72°F | 55 mm | 9 | — |
| April | 29°C / 84°F | 23°C / 73°F | 110 mm | 11 | — |
| May | 30°C / 86°F | 24°C / 75°F | 155 mm | 14 | — |
| June | 31°C / 88°F | 25°C / 77°F | 130 mm | 14 | — |
| July | 31°C / 88°F | 25°C / 77°F | 150 mm | 16 | — |
| August | 32°C / 90°F | 25°C / 77°F | 165 mm | 16 | — |
| September | 31°C / 88°F | 25°C / 77°F | 145 mm | 15 | — |
| October | 31°C / 88°F | 24°C / 75°F | 130 mm | 13 | — |
| November | 30°C / 86°F | 23°C / 73°F | 140 mm | 13 | — |
| December | 29°C / 84°F | 22°C / 72°F | 110 mm | 12 | — |
Other cities with similar September weather
🌍 See the full ranked list of climate twins for San Juan in September →
Frequently asked questions
How hot is San Juan in September?
In September, San Juan averages a high of 31°C (88°F) and a low of 25°C (77°F) — generally hot.
Does it rain a lot in San Juan in September?
September is quite rainy in San Juan, with about 15 rainy days on average.
Is September a good time to visit San Juan?
September is hot but on the rainy side. It suits travelers who are comfortable with hot weather; check the month-by-month ranking to compare it against the rest of the year.
What should I pack for San Juan in September?
Pack lightweight, breathable clothing, sunglasses and sunscreen, plus a compact umbrella or rain jacket. See the full September packing list for San Juan for a complete, climate-based checklist.
Check the live 10-day forecast and sunrise/sunset.