Los Angeles weather and climate guide

7-day forecast for Los Angeles

Tonight in Los Angeles, CA brings mostly clear. Across the 8-day outlook, highs average 71°F and lows average 55°F, ranging from 49°F to 81°F. 2 of the 8 days carry at least a 30% chance of precipitation, so keep rain gear handy.

Current conditions

Observed at LOS ANGELES DOWNTOWN (FHMC1) at 4:30 AM PST.

A Mediterranean climate, and what that really means

Only a few places on Earth have this climate: the Mediterranean basin itself, central Chile, the Cape of South Africa, southwestern Australia, and coastal California. All sit on the western edge of a continent around 30 to 40 degrees latitude, where a semi-permanent subtropical high parks offshore in summer and blocks storms entirely.

The practical result is a rainfall pattern the opposite of most of the United States. Los Angeles gets essentially no rain from May through September. Summer rainfall in downtown LA averages under a tenth of an inch for the entire season — measurable rain in July is genuinely newsworthy. Then the high pressure retreats south in late fall, the storm track drops down, and nearly the whole annual total arrives in about five months.

That concentration is why California swings between drought and flood rather than settling into an average. A single strong atmospheric river can deliver a third of the yearly total in three days, and a winter where the storm track stays north can deliver almost nothing at all. The fourteen-inch annual figure is a long-term mean that individual years rarely resemble.

The marine layer and June Gloom

The cold California Current runs south along the coast, and sea surface temperatures off Los Angeles sit in the low 60s even in summer. Warm air above that cold water cools from below, forming a shallow deck of stratus cloud and fog usually 1,000 to 2,000 feet thick — the marine layer.

A temperature inversion caps it. Normally air cools with height, but here a layer of warm, sinking air from the subtropical high sits on top, acting like a lid. The cloud cannot rise through it, so it spreads horizontally inland overnight, then burns off through the morning as the sun heats the ground.

In May and June the pattern is at its most stubborn, producing the local phenomenon known as June Gloom: overcast mornings that may not clear until mid-afternoon, or at all near the coast, during what visitors assume will be the start of summer. Beach neighborhoods can go a week without real sunshine while Pasadena bakes ten miles inland. The gloom typically fades by July as the land warms enough to break the pattern down.

The same inversion is why Los Angeles had such severe smog before emissions controls. Pollution generated in the basin cannot escape upward through the lid, and mountains block it from moving inland, so it accumulates. Air quality has improved enormously since the 1970s, but the geography that trapped it has not changed.

Santa Ana winds and fire weather

Santa Ana winds are the region's most dangerous weather, and they arrive in autumn when high pressure builds over the Great Basin — the high desert of Nevada and Utah. Air flows from that high toward lower pressure off the California coast, moving from the desert toward the ocean, which is the reverse of the normal onshore flow.

Two things happen to that air on the way. It is already dry, and as it descends from the Great Basin's elevation down through mountain passes to sea level, compression heats it further — roughly 5 °F for every thousand feet of descent. Relative humidity can collapse into single digits. And as the flow squeezes through canyons and passes it accelerates, producing sustained winds of 40 mph with gusts above 70, occasionally over 100 in the worst events.

Hot, bone-dry air moving fast through terrain covered in chaparral that has had no rain for six months is the worst possible fire combination. Nearly every catastrophic Southern California wildfire has occurred during a Santa Ana event, because these winds throw embers a mile or more ahead of the fire front and make containment essentially impossible until the wind drops.

This is why Red Flag Warnings matter so much here, and why utilities now cut power preemptively during the strongest events. The season runs roughly September through February and peaks in December, which means the highest fire risk arrives at the end of the dry season rather than in the hottest months.

Microclimates: why the forecast depends on the block

Los Angeles County contains more distinct microclimates than any comparable area in the country. The ingredients are a cold ocean, a large basin, and mountain ranges rising above 10,000 feet, all within about sixty miles.

Distance from the ocean is the dominant factor. Every mile inland typically adds about a degree to the summer afternoon high, and the effect compounds once you cross a mountain range. On a hot August day, Santa Monica may reach 75 °F while Woodland Hills in the San Fernando Valley reaches 105 — a thirty-degree difference across fifteen miles of the same city.

Elevation adds another layer. The San Gabriel Mountains rise directly behind the basin, and Mount Baldy at 10,064 feet holds snow into spring. It is entirely possible to surf in the morning and reach a ski area in the afternoon, a cliché that happens to be true.

The practical consequence is that a single "Los Angeles forecast" is close to meaningless. Enter your actual ZIP code rather than relying on the city name, because the National Weather Service grid resolves these differences and the label "Los Angeles" does not.

Atmospheric rivers, the wet side of the extreme

When rain does come, it often arrives as an atmospheric river: a narrow corridor of concentrated water vapor thousands of miles long, streaming in from the subtropical Pacific. The strongest are informally called the Pineapple Express when they originate near Hawaii.

A single event can drop five to ten inches in the mountains over a few days. Because the ground is dry and much of the basin is paved, that water runs off almost immediately rather than soaking in, filling the concrete flood channels the region built for exactly this reason.

The worst flooding usually follows a fire. Burned slopes lose the vegetation that held soil in place, and intense rain on a recent burn scar produces debris flows — fast-moving slurries of mud, rock and vegetation. The Montecito debris flow of January 2018, weeks after the Thomas Fire, killed 23 people. If you live below a recent burn area, rain forecasts deserve as much attention as fire forecasts did.

Weather hazards to know about

• Santa Ana winds and wildfire

  September through February, peaking in December

  Sustained 40 mph winds with gusts above 70, single-digit humidity and extreme fire spread. Expect Red Flag Warnings and possible precautionary power shutoffs.

• Atmospheric rivers and flash flooding

  November through March

  Several inches of rain in days on dry, paved ground. Flood channels and normally dry washes fill fast; never drive into flowing water.

• Debris flows below burn scars

  The first two rainy seasons after any fire

  Rain rates above half an inch per hour on a recent burn scar can trigger fast-moving mud and rock flows. Evacuation orders for these are issued on rainfall forecasts, before anything happens.

• Inland heat waves

  July through October

  Valley and inland areas exceed 105 °F while the coast stays mild. Air conditioning is far less universal here than in the Southwest, which raises the health risk during long events.

What to wear and pack, by season

Spring (March to May)

Layers, and expect grey mornings by the coast. Afternoons are usually pleasant in the 70s, but a beach evening turns cool quickly.

Summer (June to August)

Light clothing, sunscreen and a light jacket or sweater for the coast after sunset. If your plans reach inland, prepare for genuine heat in the valleys.

Fall (September to November)

The warmest and clearest stretch of the year, often hotter than midsummer thanks to Santa Ana conditions. Light clothing and lip balm — the air gets extremely dry.

Winter (December to February)

A light jacket and a rain shell. Nights drop into the 40s and the rain, when it arrives, arrives seriously. Snow chains matter only if you head to the mountains, where they are sometimes required.