Rainy season prep for an Irvine home matters because the rain comes in a short window. NOAA 1991 to 2020 normals for the Irvine Ranch station show about 13.06 inches a year, with February, January and December the wettest months. Clear gutters and drains, check sliders and roof edges, and review flood coverage before the first storm.
When the Rain Actually Arrives in Irvine
NOAA's 1991 to 2020 normals for the Irvine Ranch station show about 13.06 inches of rain a year. February is the wettest month at 3.47 inches, then January at 2.67 inches and December at 2.34 inches. Santa Ana averages about 12.54 inches a year, most of it falling from November through April.
That pattern explains a lot of winter calls. Months of dry weather let leaves fill gutters, dirt build up in patio drains and roof flashing dry out unnoticed. Then a single storm puts more water on the house in a day than it saw all summer. Fall is the time to get ahead of it.
What Recent Storms Showed Orange County
Big rain here comes in bursts. On December 14, 2021, a flash flood warning covered central Orange County, with expected rain of 0.5 to 1 inch per hour. The warning included Irvine, Tustin, Laguna Beach, Newport Beach, Aliso Viejo, Laguna Woods and Laguna Hills.
OCWD reported that the February 2024 storms brought 7.28 inches of rain to the region. It captured 25,500 acre-feet, or 8.3 billion gallons, of stormwater. On February 7, 2024, parts of Orange County were under a flood watch.
Rain at that rate overwhelms anything that's partly blocked. That's when water comes in at slab edges, under sliders and through roof valleys that held fine in lighter storms.
Gutters, Downspouts and the Ground Around Your Slab
On a slab home with stucco walls, water that pools against the wall has a short path inside. It usually shows up at the bottom plate behind the baseboard. That's why your fall checklist should start outside, at ground level.
- Clear gutters and run a hose through each downspout to confirm it drains freely.
- Add extensions so downspouts empty several feet from the wall, not against the stucco.
- Lift grates on patio and yard drains and clear the dirt and leaves underneath.
- Check that soil and mulch slope away from the house, not toward it.
- Pull planters, firewood and stacked items away from the base of exterior walls.
- Run sprinklers briefly and watch where the water goes before the rain does it for you.
Water still spreading? We answer every hour of the day and night.
Call (949) 539-8184Sliders, Windows and Roof Edges Where Rain Gets In
Sliding glass doors are a common entry point in a hard storm. The track has small weep holes that let water drain back out, and they clog with dirt over a dry summer. Vacuum the track and pour a cup of water in to check that it drains outside.
Look at window corners from inside for old stains or bubbling paint, which point to a past leak. On the roof, the trouble spots are usually flashing at chimneys, vents and walls, valleys full of debris, and cracked or slipped tiles. Tile roofs shed water well, but the underlayment beneath them does the real work, and it doesn't last forever.
If you've found stains on a ceiling, deal with them before the season, not during it. Our page on roof leak water damage covers what we check inside the attic and ceiling once water has come through.
San Diego Creek, Flood Zones and Flood Insurance
San Diego Creek is the main watercourse draining Irvine. It flows northwest into Upper Newport Bay, and Peters Canyon Wash is its largest tributary. Irvine participates in the National Flood Insurance Program and keeps elevation certificates on file for properties in the special flood hazard area. If you're unsure where your home sits, ask the city whether it has a certificate for your address.
Coverage is where the surprises usually are. FloodSmart, the NFIP's consumer site, says most homeowners insurance does not cover flood damage. It also says almost one-third of NFIP flood insurance claims come from outside high-risk flood areas.
Timing matters too. NFIP guidance for agents says that in many cases a new flood policy takes effect 30 days from the date of purchase. Buying one when a storm is forecast is usually too late. This is general information, not insurance advice: your policy decides. Our post on whether homeowners insurance covers water damage goes further.
Canyon and Burn-Scar Areas Need a Different Plan
Homes near the foothill canyons face mud and debris, not just water. The December 14, 2021 storm set off mudslides in the Bond Fire burn area, and firefighters rescued trapped residents in Silverado Canyon. On February 7, 2024, a voluntary evacuation warning covered Silverado, Williams, Modjeska and Trabuco canyons.
The Orange County Sheriff keeps a debris-flow plan for the 2024 Airport Fire burn scar. As of its September 2026 update, it still covers Trabuco Creek (including the Holy Jim area), Bell Canyon and Hot Springs Canyon. If you live in one of those areas, follow the Sheriff's plan and evacuation orders first. Sandbags won't protect a house from a debris flow.
Mud that gets inside carries soil and runoff, so we treat it as contaminated water. Storm and flood cleanup starts with shoveling and hauling out the solids before extraction and drying can begin.
A Storm-Day Plan for Inside the House
Most of this takes ten minutes in October, and it'll save real damage in February. Do it once and keep the notes on your phone.
- Find the main water shutoff and make sure everyone in the house can turn it.
- Photograph each room and your larger belongings before the season, for any claim later.
- Keep old towels and a wet vacuum by the sliders that face the weather.
- Move boxes and electronics off garage and closet floors on exterior walls.
- Know which breaker feeds the rooms most likely to take water.
Questions readers ask
October or early November is a good target. Santa Ana gets most of its rain from November through April, and Irvine's wettest months are December, January and February.
It depends on how the water got in, and your policy decides. Water through a storm-damaged roof may be treated differently from rising floodwater. FloodSmart says most homeowners insurance does not cover flood damage, so check your policy with your agent.
Usually it's too late. NFIP guidance says that in many cases a new policy takes effect 30 days after purchase. Buying a new home is one of the listed exceptions.
It can be. Water at a slider often runs under the baseboard and into the bottom of the wall and the carpet pad. Pull the carpet back at the corner and check the pad, or call us to meter the wall before it sits.
Keep yourself safe, then stop what you can and move belongings out of the path. Photograph where the water entered. Call us any hour for water extraction before it spreads under floors and into walls.
Where these facts come from
- Wikipedia: Irvine, California (NOAA climate normals, San Diego Creek)
- Wikipedia: Santa Ana, California (climate)
- CBS Los Angeles: Flash flood warning for Orange County
- ABC7: Storm evacuation orders in Silverado and Williams canyons
- NBC Los Angeles: Flood watches as historic storm moves out of Southern California
- Stormwater: Orange County captures 8.3 billion gallons of stormwater in February
- Orange County Sheriff's Department: Airport Fire debris flow
- City of Irvine: Flood zone and National Flood Insurance Program
- FloodSmart: The National Flood Insurance Program
- FloodSmart for agents: Important Reminder for Your Clients