Question 1

What is the sunniest time of year in San Diego?

Accepted Answer

The sunniest time of year in San Diego is mid-to-late summer, with **July 2025 leading the way at 379.3 hours of sunshine** — about 12.2 hours of sun per day. San Diego is famous for its bright climate, and the 2025 data confirms it.

July and August were the standout months for sunshine in San Diego. July recorded 379.3 hours (roughly 12.2 hours daily), while August followed closely with 362.0 hours, averaging about 11.7 hours of sun per day. Both months were also exceptionally dry, with July seeing just 0.2 mm (0.01 in) of precipitation and comfortable mean temperatures of 19.4°C (66.9°F).

Interestingly, early summer tells a different story. June 2025 was the cloudiest month of the year, with only 173.0 hours of sunshine (about 5.8 hours per day) — a local pattern often called "June Gloom," when coastal clouds linger through the mornings. Over the full year, San Diego accumulated 3,166 hours of sunshine, averaging a generous 8.7 hours of sun each day.

For visitors planning beach days or outdoor activities, July and August offer the most reliable sunshine in San Diego, paired with warm, rain-free conditions. If you prefer to avoid the early-summer cloud cover, aim for after the first week of July rather than June, when the marine layer is most persistent.

Question 2

Which season is the wettest in San Diego?

Accepted Answer

Autumn was the wettest season in San Diego in 2025, with the meteorological autumn (September 1 to November 30) delivering 108.6 mm (4.28 in) of rain — more than any other season that year.

Breaking down the 2025 totals by meteorological season, autumn narrowly edged out spring (March to May), which recorded 99.3 mm (3.91 in). The winter portion within 2025 (January and February only) was surprisingly dry at just 23.8 mm (0.94 in), while summer (June to August) was the driest stretch with only 16.6 mm (0.65 in). Across the full year, San Diego collected 287.0 mm (11.3 in) of precipitation spread over roughly 12 rainy days.

Rainfall in San Diego tends to arrive in concentrated bursts rather than steady drizzle. November 2025 was the standout autumn month with 65.3 mm (2.57 in), and March was the single wettest month of the year at 89.1 mm (3.51 in). By contrast, July saw almost no rain at all, just 0.2 mm.

For visitors and residents, this means the autumn and spring shoulder seasons carry the highest chance of wet days in San Diego, so it's worth packing a light rain layer if you travel in September through November. Summer remains reliably dry, making it the safest bet for outdoor plans across the city.

Question 3

What was the hottest day in San Diego in 2025?

Accepted Answer

The hottest day in San Diego in 2025 was **August 23**, when the temperature peaked at **37.1°C (98.8°F)** — by far the warmest reading of the year.

That day stood out sharply from the rest of 2025. The next-hottest days reached only about 33.5°C (92.3°F) on May 10 and 32.8°C (91.0°F) on October 29, so San Diego's August 23 high cleared the runner-up by more than 3.5°C (6°F). On the record day itself, the temperature still dropped to a mild low of 18.3°C (64.9°F), giving a daily average of 24.8°C (76.6°F) with humidity around 74%.

Such heat is genuinely rare for the city. Across all of 2025, San Diego recorded just 8 days at or above 30°C (86°F) and only 6 days at or above 32°C (89.6°F). For most of the year, conditions stayed far milder, with an average daily high of 21.9°C (71.4°F).

August was the warmest month overall, averaging highs of 26.7°C (80.1°F), so brief spikes like this one typically arrive in late summer when offshore winds push hot, dry air toward the coast. If you're visiting San Diego, days above 35°C (95°F) are the exception rather than the rule — the coastal climate keeps temperatures comfortable nearly year-round, making the August 23, 2025 record a notable outlier worth planning around only if you're heat-sensitive.

Question 4

How much does the temperature vary throughout the year in San Diego?

Accepted Answer

San Diego has one of the most stable year-round climates in the United States, with average monthly temperatures shifting by only about 8.8°C (15.8°F) across all of 2025. The city's mild, ocean-moderated weather means there is no extreme hot or cold season the way inland cities experience.

In 2025, the coolest month was January, with an average temperature of 12.6°C (54.7°F), while the warmest was September at 21.4°C (70.5°F). Averaged across the full year, San Diego sat at a comfortable 16.9°C (62.3°F).

Day-to-day extremes were wider than the monthly averages suggest. The warmest reading of the year came during a late-summer heat event in August, reaching 37.1°C (98.8°F), while the coldest morning low dipped to 4.8°C (40.6°F) in January. That gives a full observed span of about 32.3°C (58.1°F) between the year's hottest afternoon and coldest night.

A few practical takeaways for San Diego:

- **No real winter freeze:** even the coldest month averaged well above 12°C (54°F).
- **Gentle warming curve:** temperatures climb gradually from spring into a late-summer peak in August and September.
- **Brief heat spikes:** occasional inland-influenced days can push past 35°C (95°F), so light layers are useful even in summer.

This narrow seasonal swing makes San Diego a reliable year-round destination, with comfortable conditions for sightseeing, beach trips, and outdoor activities in nearly every month of the year.

Question 5

What is the weather like in San Diego in December?

Accepted Answer

December in San Diego is mild and mostly dry, with average daytime highs around 21.8°C (71.2°F) and cool nights near 10.5°C (50.9°F). The overall mean temperature for the month in 2025 was 15.4°C (59.8°F), making it one of the most comfortable winter destinations in the United States.

December 2025 in San Diego delivered plenty of sunshine alongside occasional rain:

- **Sunshine:** about 236 total hours, averaging 7.6 hours of sun per day
- **Rainfall:** 38.4 mm (1.51 in) of precipitation across just 6 rainy days, leaving 25 dry days
- **Warmest day:** a high of 29.2°C (84.6°F) on December 9, 2025
- **Coolest night:** a low of 5.8°C (42.4°F) on December 5, 2025

Humidity averaged a moderate 71.7%, and winds stayed gentle at roughly 7.6 km/h (4.7 mph), so conditions rarely felt harsh. Most of the rain arrived in short bursts late in the month, with the wettest day bringing 15.1 mm (0.59 in) on December 31, 2025.

For visitors, December weather in San Diego means you can comfortably plan outdoor sightseeing, beach walks, and dining on most days. Pack layers for the cool evenings and a light jacket, but expect far more sun than rain. With abundant dry days and pleasant afternoon temperatures, San Diego remains an appealing winter-getaway climate throughout December.

San Diego

California

FAQ

What is the sunniest time of year in San Diego?

Which season is the wettest in San Diego?

What was the hottest day in San Diego in 2025?

How much does the temperature vary throughout the year in San Diego?

What is the weather like in San Diego in December?