San Diego in September
In September, San Diego averages 26°C (78°F) during the day and 18°C (65°F) at night, with around 5 days of rain (11 mm total).
High seasonConditions are comfortable for sightseeing without being sweltering. Occasional showers are likely but won't dominate.
It's peak hurricane season in San Diego 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 Diego
September is one of the warmest months in San Diego (1st of 12) and moderately rainy compared to the rest of the year (8th of 12). Daytime temperature runs 4°C above the annual average (21°C). September runs roughly the same as August (26°C) and cools 1°C in October (24°C).
September sunrise & sunset in San Diego
Times shown for San Diego local time (America/Los_Angeles), calculated for the 15th of September. They shift by a few minutes day to day across the month.
Photography light in San Diego — September
Golden-hour and blue-hour windows for the 15th of September, in San Diego's local time. Use these for soft warm light (golden) or cool architectural twilight (blue).
📅 When to book — San Diego 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 (High season) and San Diego's popularity.
Crowds & pricing — September in San Diego
This is a busy month in San Diego — not the absolute peak, but tourist numbers are clearly elevated. You'll feel it at headline attractions on weekends and in the historic centre, though side streets and lesser-known sights stay manageable. Prices are above off-season but not at their summit. A good week for first-time visitors who want everything open without the worst of the crush.
Why this tier: excellent tourism weather beach-season conditions peak hazard season (1 active)
Sun & mosquito risk — September in San Diego
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 Diego — September
Across the year San Diego's sea swings from 14.7°C (February) to 21.5°C (August) — September sits at 21.1°C.
San Diego in other months
| Month | Avg high | Avg low | Rainfall | Rain days | Snow days |
|---|---|---|---|---|---|
| January | 18°C / 64°F | 9°C / 48°F | 62 mm | 8 | — |
| February | 18°C / 65°F | 9°C / 48°F | 48 mm | 8 | — |
| March | 19°C / 65°F | 11°C / 51°F | 44 mm | 11 | — |
| April | 20°C / 68°F | 13°C / 55°F | 22 mm | 8 | — |
| May | 20°C / 68°F | 14°C / 58°F | 16 mm | 9 | — |
| June | 22°C / 72°F | 16°C / 61°F | 2 mm | 4 | — |
| July | 25°C / 76°F | 18°C / 65°F | 5 mm | 2 | — |
| August | 26°C / 78°F | 19°C / 66°F | 9 mm | 3 | — |
| September | 26°C / 78°F | 18°C / 65°F | 11 mm | 5 | — |
| October | 24°C / 76°F | 16°C / 60°F | 10 mm | 5 | — |
| November | 21°C / 70°F | 12°C / 53°F | 28 mm | 6 | — |
| December | 18°C / 64°F | 9°C / 48°F | 63 mm | 8 | — |
Other cities with similar September weather
🌍 See the full ranked list of climate twins for San Diego in September →
Frequently asked questions
How hot is San Diego in September?
In September, San Diego averages a high of 26°C (78°F) and a low of 18°C (65°F) — generally warm.
Does it rain a lot in San Diego in September?
September sees occasional rain in San Diego, with about 5 rainy days on average.
Is September a good time to visit San Diego?
September is warm and mostly dry. It suits travelers who are comfortable with warm weather; check the month-by-month ranking to compare it against the rest of the year.
What should I pack for San Diego in September?
Pack light layers for warm days and cooler evenings. See the full September packing list for San Diego for a complete, climate-based checklist.
Check the live 10-day forecast and sunrise/sunset.