Prepare Your Roof for the Los Angeles Rainy Season

This page is the pre-season list only, not leak tracing or prices; upkeep through the rest of the year is in the annual roof maintenance checklist, the warning signs in depth are in signs you need a new roof, and the decision after an inspection is in roof repair or replace; when in the year a replacement fits is in the best time to replace a roof in Los Angeles. The parts of a roof guide names each part mentioned here.

Source: NOAA NCEI 1991–2020 monthly normals for Los Angeles Downtown (USC campus), Burbank–Glendale–Pasadena Airport, Van Nuys Airport and Los Angeles International Airport. Normals are long-term averages, not a forecast, and any one year can be much wetter or drier; for Burbank and Van Nuys NOAA computes them from 19 to 23 years of records rather than the full 30.

What the table shows:

• The rain is packed into five months. At all four stations, about 87% of a normal year falls from November through March. December through March are the wettest months, and February has the highest normal at every station.
• Summer is close to dry. June through September together average about a fifth to a quarter of an inch. A roof can go four months without a real test.
• The season opens in October. All four stations average about two days in October with measurable rain (0.01 inch or more), against about half a day in September. Downtown averages about one October day with a tenth of an inch or more, closer to two in November, and three to five a month from December through March. So aim to finish roof work by mid-October, and by the end of October at the latest, before the wet months start.

• Leaves, needles, seed pods and dust collect in the gutters and downspouts, in the valleys (the inside corners where two roof slopes meet), and behind chimneys and skylights, and nothing washes them out.
• Sun and heat age the covering. Sealant around pipes and flashings dries and cracks, and rubber pipe boots split.
• Fall Santa Ana winds can lift shingles and shift tiles or flashing just before the rain; what to check after a windstorm is in Santa Ana winds and your roof.
• A small opening can't leak until water reaches it.

So a roof that looked fine all summer can drip in the first storm, and a gutter or roof drain that filled up over the summer overflows the first time it has to carry real water.

What you can do from the ground and the attic

Gutters and downspouts. Clear the debris out of the gutters and make sure each downspout is open top to bottom. Then run a garden hose into the gutter at the end farthest from the downspout and look for water spilling over the edge, dripping behind the gutter, leaking at joints, or not coming out at the bottom. A gutter that sags or pulls away from the fascia needs rehanging, and a soft or stained fascia behind it is covered in dry rot in fascia, eaves and roof sheathing. On a one-story house you can often reach the gutters from a sturdy ladder on firm, level ground. On a two-story house, or anywhere you'd be working high on a ladder, hire it out. Keep the ladder well clear of the power line to the house, and never step off the ladder onto the roof. Where downspouts should send the water, and whether a house needs gutters at all, is in do you need gutters in Los Angeles?.

Downspout outlets. Water should land on a splash block or in an extension that carries it away from the house, not into a planter bed against the wall. If a downspout feeds an underground drain, clear the inlet and check that water comes out at the other end. Pointing downspouts away from the house is good practice anywhere. Where expansive or collapsible soils are known to exist, the building code requires houses to discharge roof water to the ground at least 5 feet from the foundation walls, or into an approved drainage system (California Residential Code, CRC 2025, R801.3).

Trees over the roof. Branches over the roof drop leaves and needles into the gutters and valleys and can scrape the covering in wind. Have them trimmed back, and leave anything large or high to a tree service. If a branch is anywhere near a power line, including the line from the pole to your house, don't touch it; call your electric utility.

A look at the roof with binoculars. Walk around the house and look at each slope: needles piled in valleys and behind the chimney, cracked or slipped tiles, lifted or missing shingles, loose flashing, debris banked against a skylight. Photograph anything that looks wrong. You're building the roofer's list, not diagnosing; signs you need a new roof covers what each sign can point to.

The attic, before the first rain. Take a flashlight and step only on the framing; the ceiling between the joists won't hold you. September attics get very hot by midday, so do this first thing. Look at the underside of the roof boards and rafters, especially around the chimney, vent pipes and skylights and under the valleys, for old stains, dark or soft wood, and wet or matted insulation. Mark the edge of any stain in pencil and photograph it, so after the first real rain you can tell whether it has grown.

Skylights and chimney, from inside. Check the ceiling and the skylight shafts for stains or peeling paint, and the walls around the chimney. Point out anything you find to the roofer.

The breaker panel. Know where it is and which breakers feed the top-floor lights and ceiling fans.

What to have a roofer check

• Debris on the roof itself. Leaves and needles in valleys, behind chimneys and around skylights hold water against the covering and can push it sideways under shingles or tile. Clearing them means working on the roof.
• Flashings. The metal at the chimney, walls, skylights and valleys: rust, edges lifting away from the roof, open joints, or layers of sealant built up where someone has patched before.
• Pipe boots and penetrations. The collars around plumbing vents and other pipes, and the sealant at everything that passes through the roof, such as vents, flues and mounts.
• Tile. Have broken or slipped tiles replaced before the rain. On a tile roof the waterproofing is the sheet under the tile, which the pre-season check can't see from the ground; a roofer can lift tiles to look underneath where there's a reason to.
• Flat and low-slope sections. Drains, scuppers and the surface, as described below.
• Gutters you can't reach safely, and anything you photographed from the ground or in the attic.

Flat roofs and roof drains

A garage, patio cover, porch or addition often has its own flat or low-slope roof, even when the main house is pitched. Where water doesn't run off the edges, it leaves through a few drains or scuppers (openings through the low wall at the roof edge), so a single clog can hold water on the whole roof. Before the season, have the drains and scuppers cleared, and have the surface checked for ponding marks (rings of dirt where water stood after past rains), blisters, cracks and split seams. How those outlets work is in flat roof drains, scuppers and crickets.

The code sets how these roofs must drain. Under the California Residential Code (CRC 2025, R903.4), unless a roof is sloped to drain over its edges, roof drains must be installed at each low point. Where the roof edge rises above the roof, as with a parapet, and water would be trapped if the main drains backed up, R903.4.1 also requires secondary (emergency overflow) roof drains or scuppers. Those overflow outlets need clearing too: they're the water's way out when a main drain is blocked. If a flat section behind a parapet has only one drain and no overflow outlet, point that out to the roofer before the season: one clog can then hold water on the roof until it finds a way in. Low-slope roofs, including under solar have their own guide, and the systems used to re-cover a flat roof are compared in flat roof options for Los Angeles homes.

• Remove the part of any tree within 10 feet of the outlet of a chimney or stovepipe.
• Keep trees and plants next to or overhanging the building free of dead or dying wood.
• Keep the roof clear. Both laws say it plainly: "Maintain the roof of a structure free of leaves, needles, or other vegetative materials."

The leaves and needles that clog gutters in the rain are the same material embers can ignite in a fire, so one job covers both. To check whether your address is in a zone, look it up on the State Fire Marshal's Fire Hazard Severity Zone maps and on your city's or county's zone map as well, since a city can add zones; zone lines don't follow ZIP codes.

The state's rules for Zone 0, the first 5 feet around a house, would add the gutters and the live branches over the roof to that list; as of October 2026 they were still a draft. Where they stand is in Zone 0 and your roof.

If you're replacing gutters in a Fire Hazard Severity Zone covered by the 2025 California Wildland-Urban Interface Code, section 504.4 applies: new gutters and downspouts must be noncombustible, and gutters need an approved means to keep leaves and debris from building up. More in fire zones and the 2025 WUI code.

1. September to early October. Trim the trees, clean the gutters or book someone to, point the downspouts away from the house, look in the attic, take your photos, and book the roofer's check.
2. By mid-October, end of October at the latest. Repairs finished: flashings, pipe boots, sealant, broken tiles, cleared valleys and flat-roof drains. That work goes best on a dry roof, and booking before the rain lets the roofer fix what they find instead of covering a leak first and repairing it later.
3. During the first real rain. From the ground, under cover, watch the gutters and downspouts. Water spilling over the edge, or nothing coming out at the bottom, points to a clog or a gutter that sags or slopes the wrong way.
4. After the first real storm. Go back into the attic and compare with your pencil marks and photos, and check the top-floor ceilings. A stain that has grown, fresh damp or a new drip means an active leak: call the roofer while it's small.

• Catch the water in a bucket and move furniture and electronics out of the way.
• If the drip is at a light fixture or ceiling fan, turn that circuit off at the panel and leave the fixture alone.
• Don't go up on the roof in the rain or while it's wet, and don't try to tarp it yourself. Call a roofer, who can cover it until it's repaired.
• Photograph the drip and the ceiling, and note when it started and how hard it was raining.

What to do in order, including a sagging ceiling, the insurer and drying out, is in what to do when the roof leaks in a storm; how to narrow down where the water gets in is in how to find a roof leak.

Code sections, rules and figures on this page come from the primary sources below. Codes, local requirements and product terms change; each was verified October 9, 2026.

1. NOAA NCEI, U.S. Climate Normals 1991–2020 (monthly)
2. NOAA NCEI monthly normals, Los Angeles Downtown USC (USW00093134)
3. NOAA NCEI monthly normals, Burbank–Glendale–Pasadena Airport (USW00023152)
4. NOAA NCEI monthly normals, Van Nuys Airport (USW00023130)
5. NOAA NCEI monthly normals, Los Angeles International Airport (USW00023174)
6. California Residential Code 2025, Chapter 9 Roof Assemblies, R903.4 (UpCodes)
7. California Residential Code 2025, Chapter 8 Roof-Ceiling Construction, R801.3 (UpCodes)
8. California Public Resources Code §4291
9. California Government Code §51182
10. California Wildland-Urban Interface Code 2025, Chapter 5 (UpCodes)
11. Office of the State Fire Marshal, Fire Hazard Severity Zones