California is once again being drenched by an atmospheric river-driven storm — but by the time a storm is in the forecast, it’s most often too late for homeowners to buy flood insurance.

But it’s not too late to protect against future storms. Just 185,000 Californians have flood insurance through the nation’s largest flood insurer — leaving millions of people exposed in the event of a mega storm sequence that produces a modern equivalent of the Great Flood of 1862, or even for more minor flood damage caused by winter storms.

Here are six things experts think you should know about flood insurance.

What does flood insurance cover?
Typical homeowners insurance covers many types of storm damage, including hail damaging your roof or trees falling onto a home. But it won’t protect against damage caused by an overflowing river or street flooding.

Whenever water rises from the ground, it’s considered flooding, according to Janet Ruiz, spokesperson for the Insurance Information Institute.

Perhaps surprisingly, flood insurance also covers mudslides after wildfires, which do not fall under a typical homeowners policy.

Ruiz encouraged homeowners to speak with their insurance agent or broker about exactly what their policy covers. Some home insurance policies may offer limited coverage for sewage backup or sump pump backups during heavy rain, she said — and some insurers may allow homeowners to purchase additional coverage for sewage.

Who should sign up for flood insurance?
Having flood insurance isn’t required unless you have a mortgage through a government-backed lender and are living in a Federal Emergency Management Agency-defined special flood hazard area. But that doesn’t mean those who aren’t required to buy flood insurance shouldn’t look into it — about 25% of flood insurance claims come from those living outside of flood zones, according to FEMA.

In 2020, ProPublica reported there could be millions of properties across the U.S. that are at high risk of flooding but aren’t located in a FEMA hazard zone.

“People tend to think that unless they’re living on the bank of a river or right on the beach that they don’t need flood insurance. Increasingly, experts know that’s not true,” said Amy Bach, founder of the consumer advocacy organization United Policyholders.

Homes that have flood risk mitigation measures — such as those with elevated foundations or stilts — may not need to buy flood insurance, according to Ruiz.

What is the waiting period for coverage?
The National Flood Insurance Program (NFIP), a federal insurance program run by FEMA, requires a 30-day waiting period for new policies. In a very narrow set of cases, homeowners in high risk areas may be able to get an exception and only wait one day for coverage to start.

Residents can contact their local insurance broker or search for their address on FEMA’s website to determine if they live in a high-risk area and could be subject to the one-day waiting period.

Private insurers’ waiting periods may vary, but many may decline to take on new customers if a storm is already happening or is likely to hit, Ruiz said.

How do I sign up?
The National Flood Insurance Program offers direct sales of insurance and also partners with insurance companies to provide coverage to their clients. It’s the largest flood insurer in the U.S. Still, only about 185,000 Californians purchased flood insurance in 2023, far fewer than the more than eight million dwellings with a homeowners policy in the state, according to data from FEMA and the California Department of Insurance.

Several private insurance companies, including Liberty Mutual and Allstate, also offer their own flood insurance policies. In 2023, private flood insurers wrote about $71 million in premiums in California compared to the NFIP’s about $167 million.

Policies through the NFIP offer up to $250,000 of coverage for damage to the building and up to $100,000 of coverage for personal contents. Increased coverage limits are available on the private market, Ruiz said.

To get a quote for flood insurance, you can search for insurers online or contact your normal home insurance broker. Most brokers are authorized to write policies with the NFIP and may be able to write a private flood policy or refer you to someone who can, Ruiz said.

How much does flood insurance cost?
Data from the NFIP shows that in 2023, 40% of California flood insurance policyholders paid less than $1,000 for their policy, and another 32% paid between $1,000 and $2,000.

Areas that participate in the NFIP’s community rating system may also qualify for discounts for living in a place that has undergone mitigation efforts, NFIP Senior Executive David Maurstad told Bach in a March interview about tips for consumers. As of 2023, there were 22,600 communities participating in the program, Maurstad said.

Prices on the private market vary but may in many cases be cheaper than the NFIP, according to Ruiz.

Bach encouraged homeowners to shop around. Coverage for homes with flood mitigation such as elevated foundations or for homes located in low-risk areas is often cheap and worth it in order to protect your most important asset, both experts said.

“Get a quote for flood insurance, even if you don’t think you need it, just to find out what it is. Because every day that goes by now, more and more areas are flooding that have never flooded,” she said.

What should I do if my home is damaged by a storm?
Whenever water damage happens to your home, it’s important to act quickly, Ruiz said.

Leaving water to sit may lead to mold, creating even more costly damage. The NFIP has a 60-day deadline for submitting claims after a disaster.

If your home insurance company denies coverage on the basis that the damage was caused by flooding, and you don’t have flood insurance, Bach recommended consulting with a structural engineer or forensic construction expert. Either can help determine what caused the damage and may be able to convince your company to provide coverage if the damage was not due to flooding, she said.

But the easiest thing by far is to prevent storm damage from happening in the first place, Ruiz advised. She encouraged homeowners to look up where to pick up sandbags in their area before a storm. When storms happen, homeowners should observe where water pools on their property and take steps to prevent water from getting into their home.

The Insurance Institute for Business and Home Safety offers additional tips on what to do to protect your home when flooding is imminent.