If you’ve ever stood on the corner of Market and Powell during a January "Atmospheric River," you know that San Francisco rainfall totals aren't just numbers on a spreadsheet. They are a mood. They are a logistical nightmare for Muni. Honestly, they’re the difference between a lush, green Presidio and a dry, brown tinderbox by July. But if you look at the official gauge downtown, you might get a totally different story than someone living out by Ocean Beach.
San Francisco is weird.
The city’s climate is famously fractured by its topography. While the National Weather Service (NWS) keeps the official tally at downtown locations—currently at a sensor near the Old Mint—those figures frequently fail to capture the reality of the Sunset District or the peaks of Twin Peaks.
Rain here doesn't fall evenly. It's chunky. It’s sporadic. And lately, it’s been downright chaotic.
Understanding the "Average" San Francisco Rainfall Totals
We talk about "normal" a lot in meteorology. For San Francisco, the 30-year climate normal (currently spanning 1991–2020) sits at approximately 22.89 inches annually. That sounds straightforward, right? It isn't.
In a city defined by microclimates, that 22-inch figure is basically a rough estimate. If you’re tucked into the eastern shadow of Mount Davidson, you might see several inches less than the folks catching the brunt of the Pacific moisture on the western slopes. This isn't just a minor discrepancy. Over the course of a season, the gap between the wettest and driest blocks in the city can be 5 to 10 inches.
Most of this water arrives in a very tight window. We get almost nothing from June through September. Our entire water budget is decided between November and March. If the "storm door" doesn't open by Christmas, people start getting nervous about droughts. If it stays open too long, we’re looking at sinkholes in the Marina.
The Atmospheric River Factor
When you see a spike in San Francisco rainfall totals, it's usually thanks to an Atmospheric River (AR). These are basically fire hoses in the sky. They carry more water than the mouth of the Mississippi River, stretching all the way from the tropics near Hawaii—hence the "Pineapple Express" nickname.
Dr. Marty Ralph from the Center for Western Weather and Water Extremes (CW3E) has spent years categorizing these. They range from AR-1 (beneficial) to AR-5 (hazardous). When an AR-4 hits the Bay Area, we aren't just talking about a rainy day. We’re talking about three inches of rain in 24 hours. That kind of intensity overwhelms our 19th-century combined sewer system, leading to those infamous videos of geysers shooting out of manhole covers in the Mission District.
A Look at the Record Breakers
History is messy.
The wettest "rain year" (which runs from July 1 to June 30) ever recorded in San Francisco was 1861–1862. It dumped a staggering 49.27 inches on the city. That was the year of the Great Flood of California, which literally turned the Central Valley into an inland sea. It’s the benchmark for disaster.
More recently, the 2022–2023 season reminded everyone that the drought-to-deluge pipeline is real. San Francisco saw over 32 inches that year. It felt like it never stopped. Every week brought another "bomb cyclone." On December 31, 2022, the city recorded its second-wettest day in history with 5.46 inches in a single 24-hour period. Just think about that. Five inches. In one day.
Contrast that with the "Year of No Rain" (not literally, but close). In 2013–2014, the city barely scraped together 7.93 inches. When you live in a place where the difference between the record high and the record low is 40 inches, you realize that "average" is just a mathematical fiction. Nobody actually experiences an average year.
Why the Location of the Gauge Matters
For a long time, the official records were kept at Federal Office Building. Then they moved. Every time the gauge moves, the historical continuity gets a little bit twitchy.
The current official station is known as Downtown San Francisco (SFOC1).
Because San Francisco is only seven by seven miles, you’d think one gauge is enough. It's not. The "Fog Shadow" is real. When rain clouds hit the coastal hills, they undergo orographic lift. They dump more rain on the windward side. By the time those clouds reach the East Cut or SoMa, they’ve squeezed out a good portion of their moisture. If you’re checking San Francisco rainfall totals to decide if you need an umbrella in Dogpatch, the downtown gauge is usually "close enough," but it’s rarely perfect.
The Impact of a "Wet" Year on City Life
When the totals start creeping toward the 30-inch mark, the city changes.
The hills in Glen Canyon Park turn a shade of green that looks almost neon. It’s beautiful, but it’s also a warning. Saturated soil in San Francisco is a recipe for mudslides. We saw this on Caselli Avenue and in the Berkeley Hills (just across the bay) during the heavy rains of early 2023 and 2024. Tree limbs—especially from those massive, shallow-rooted Blue Gum Eucalyptuses—start coming down once the ground gets "soupy."
There is also the salinity factor in the Bay. Massive rain totals flush out the Delta. The freshwater plume pushes further into the Bay, which affects everything from Dungeness crab migrations to the local herring runs.
- Infrastructure Strain: The city has a "Combined Sewer System." This means storm runoff and raw sewage go into the same pipes. During extreme rainfall, the plants can't keep up. The result? "Bypasses" where partially treated water is released into the Bay.
- Economic Shifts: Construction stops. Outdoor dining (a post-2020 staple) vanishes. However, the ski resorts in the Sierras—which rely on the same storm tracks—see a massive boom.
- The Reservoir Reality: While local rain is great for the backyard, the rain that actually matters for your tap water falls 150 miles away in the Hetch Hetchy watershed.
Predicting the Unpredictable: El Niño and La Niña
You've heard the terms. El Niño usually means a wetter-than-average winter for California, while La Niña suggests a drier one. But for San Francisco, the correlation is actually pretty weak.
The city sits at a transition point. Northern California often benefits from La Niña storms, while Southern California gets soaked by El Niño. San Francisco is stuck in the middle. We've had bone-dry El Niño years and record-breaking La Niña years. Meteorologists like Jan Null of Golden Gate Weather Services often point out that "ENSO" (El Niño Southern Oscillation) is just one of many drivers. The "Ridging Triple Threat" or the "Blob" in the Pacific can easily override those tropical signals.
Essentially, don't bet your mortgage on an El Niño forecast.
Climate Change and the "Whiplash" Effect
Evidence suggests that while the total volume of rain might not change drastically over a century, the delivery is becoming more violent. We are seeing longer dry spells followed by more intense bursts.
Climate scientists call this "weather whiplash."
Instead of 22 inches spread out over 40 rainy days, we’re getting 20 inches crammed into 15 days. This is bad for the soil. It’s bad for the reservoirs. And it makes tracking San Francisco rainfall totals much more stressful for city planners who have to manage the sudden influx of water.
How to Track Local Rain Like a Pro
If you actually live here, or you're planning a trip and don't want to get soaked, stop looking at the generic weather app on your phone. They usually use a single data point that might be miles from your actual location.
- Check CNRFC: The California Nevada River Forecast Center provides real-time "gridded" precip maps. It shows you exactly where the rain is hitting.
- Find a WeatherStem or Personal Weather Station (PWS): Sites like Weather Underground allow you to see data from people's backyards. There are hundreds of these in SF.
- Look at the "Storm to Date" vs. "Season to Date": A storm might feel big, but it’s the seasonal total that tells you if we’re actually recovering from a drought.
Actionable Steps for Dealing with SF Rain
If the San Francisco rainfall totals are trending high this week, you need a plan.
First, clear your storm drains. If there’s a pile of leaves in the gutter in front of your house, that water is going into your garage, not the sewer. The city’s "Adopt-a-Drain" program is actually a great way to stay on top of this.
Second, check your roof and gutters before November. Once the rain starts, every roofer in the Bay Area will be booked until May.
Third, understand the "3-day rule." After a major rain event where totals exceed half an inch, stay out of the ocean. The runoff from the city streets—filled with oil, trash, and that sewer overflow we mentioned—makes the water at Ocean Beach and Baker Beach pretty nasty for about 72 hours.
Fourth, keep an eye on the "Sierra Snowpack." While we track rainfall in the city for local flooding and garden health, our actual survival depends on the snow in the mountains. A "wet" SF year usually means a "big" snow year, which is the "frozen reservoir" that keeps our showers running through October.
The totals are more than just a metric. They are the pulse of the city. Whether we’re parched and praying for a "March Miracle" or sandbagging our front doors in January, the rain defines life in the 7x7. Stop looking at the average and start looking at the trends. In San Francisco, the extremes are the only thing you can truly count on.