San Francisco Weather Guide: A Complete Monthly Overview

Overview

San Francisco boasts a Mediterranean climate characterized by mild temperatures year-round and minimal seasonal variation. The city experiences average highs of approximately 14–15°C (57–59°F) in January and 22–23°C (71–73°F) in September, meaning visitors can enjoy weather similar to Seoul’s spring months (March–May) throughout the entire year.

The city’s climate presents two distinct precipitation patterns: summers (May–October) are remarkably dry with virtually no rainfall, but are heavily influenced by the California Current, creating the city’s signature fog that keeps temperatures cool. Winters (November–April), conversely, concentrate roughly 600mm of annual rainfall across these months.

The optimal travel period is September through November, when clear, warm weather prevails and fog is minimal. Summer months (June–August) should be approached cautiously due to persistent fog and cool temperatures, while winter (December–February) frequently brings rain, making waterproof jackets and layered clothing essential.

Seasonal Weather Breakdown

Spring (March–May)

Spring marks the transition from winter’s wet season to warmer, drier conditions, with average temperatures ranging from 10–18°C (50–64°F). March still receives approximately 83mm of rainfall, but precipitation drops significantly from April onward. Clear, pleasant days dominate the forecast, and from mid-April, dry weather becomes the norm.

Mornings and evenings remain cool, requiring light jackets and long-sleeved shirts as standard attire. Spring represents an excellent window to visit before summer fog sets in, with daylight hours increasing to 7–9 hours daily, making outdoor activities highly feasible.

Recommended clothing: Light jacket, cardigan, long-sleeved shirt, jeans, sneakers, sunscreen.

Summer (June–August)

Summer is best described in a single word: “fog.” Despite the season, San Francisco’s summer average temperatures of 12–20°C (53–68°F) are the coolest among major U.S. cities. Marine layer fog frequently blankets the city, leaving mornings and evenings overcast and cool, with midday sunshine often obscured by mist.

Average highs progress from 20°C (68°F) in June to 21°C (70°F) in July and 22°C (72°F) in August—sometimes feeling colder than winter months. Precipitation is negligible (less than 4mm monthly), resulting in exceptionally dry conditions. However, ocean water temperatures remain too cold for comfortable swimming.

Recommended clothing: Long-sleeved shirt, thin jacket, jeans, sneakers, sunglasses, hat, sunscreen.

Fall (September–November)

Autumn represents San Francisco’s premier travel season. Average temperatures span 13–22°C (55–72°F), with clear skies and the summer fog finally dissipating. September emerges as the warmest month at 22–23°C (72–73°F), with abundant sunny days providing ideal travel conditions.

Precipitation remains minimal (7–25mm across the season), supporting outdoor tourism and recreational activities. Daylight hours extend to 8–9 hours daily. However, as November approaches, temperatures decline and rainfall increases to approximately 67mm, necessitating light rain gear and warmer clothing layers.

Recommended clothing: Light cardigan or thin jacket, jeans, sneakers, sunglasses, hat, sunscreen.

Winter (December–February)

Winter is San Francisco’s rainy season, with average temperatures between 8–15°C (46–59°F). December and January record the highest precipitation, with 97mm and 112mm respectively. While snow is virtually nonexistent, high humidity and strong winds create a significantly lower perceived temperature.

With only 5–6 hours of daily sunlight, gray, overcast conditions persist. Visitors should pack umbrellas, waterproof jackets, and warm clothing, and should monitor weather forecasts before outings. Planning indoor attractions is advisable during this period.

Recommended clothing: Waterproof jacket, warm coat, sweater, thick pants, boots, scarf, hat, gloves, umbrella.

Month-by-Month Weather & Attire Guide

Best Times to Visit San Francisco

Optimal Period: September–November (Fall)

The autumn season represents San Francisco’s ideal visitation window. Clear, warm weather persists with average highs of 18–23°C (64–73°F) and minimal precipitation (5–76mm total). Particularly September and October stand out, offering the warmest, clearest conditions of the year while post-summer crowds diminish, ensuring comfortable, uncrowded tourism experiences.

Secondary Option: April–May (Late Spring)

Spring’s latter half provides excellent alternatives. Winter rainfall subsides, temperatures rise, and precipitation remains minimal (12–36mm), supporting outdoor recreational activities effectively.

Periods to Avoid

Summer (June–August): Despite warm expectations, average temperatures of 12–20°C (53–68°F) and persistent dense fog create suboptimal tourism conditions.

Winter (December–February): Precipitation levels of 80–114mm, with frequent rain requiring umbrellas and waterproof clothing as essentials.

Frequently Asked Questions

1. Is summer the warmest season?
   A. No—this is San Francisco’s distinctive characteristic. September is actually the warmest month (average high of 24°C/76°F), while summers are cool and foggy. These months are colloquially called “June Gloom,” “No Sky July,” and “Fogust.”
2. When is fog most prevalent?
   A. Fog is common from May through October, with June experiencing the densest conditions. August, known as “Fogust,” marks peak fog season.
3. How long does fog persist daily?
   A. In coastal neighborhoods, fog can last all day. Typically, it lingers from morning through early evening (5–6 PM), though neighborhoods like Sunset and Richmond may remain fog-covered throughout the day.
4. Is an umbrella necessary?
   A. During May–October, umbrellas are rarely needed. However, during the rainy season (November–March), a compact umbrella is strongly recommended.