Californians know wildfires and earthquakes; hurricanes, not so much. So, when Tropical Storm Hilary inundated Southern California in normally bone-dry August, it showed just how exposed homeowners are to a growing financial risk from unpredictable climate-driven flooding.

Standard homeowners insurance policies don’t cover flooding, and fewer than 2 percent of California households have flood insurance, even as intensifying winter storms overflow rivers and levees, batter the coast, and drench the desert. As Hilary, the first tropical storm to strike the Golden State in 84 years, passed over Palm Springs on Aug. 20, it dumped nearly a year’s worth of rain in a day on the desert community east of Los Angeles, causing widespread flooding in the surrounding Coachella Valley.

“Nowhere is safe from flooding in California today,” said Firas Saleh, director of product management at risk modeler Moody’s RMS. Even communities far from rivers and the coast face increasing peril. “Rainfall can happen anywhere,” added Saleh, who analyzes climate-related flood risk. “That means that these areas are becoming more and more vulnerable to flooding because of the change in the frequency and intensity of rainfall.”

Here’s what to know about flood risk and options to mitigate that exposure.

Why do so few Californians have flood insurance?

When you buy a house, the lender will check maps published by the Federal Emergency Management (FEMA) to see whether the property sits in a flood zone designated as high risk by the government. If so, the lender may require you to obtain coverage through FEMA’s National Flood Insurance Program or from a private insurer. If you have a federally insured loan and live in a hazard zone, flood insurance is mandatory. Your home may also be located in a zone FEMA identifies as at lower risk from flooding.

But given California’s exorbitant home prices and rising insurance rates, many homeowners forgo flood insurance absent a requirement to purchase polices, according to Saleh. Even those who must buy flood insurance to obtain a mortgage may cancel in succeeding years, betting their lender won’t notice. California’s record-breaking, three-year drought, which only ended with the past winter’s record-breaking storms, may have also made flooding seem like a distant threat.

The National Flood Insurance Program writes 89 percent of residential policies in California though private insurance accounts for 42 percent of premiums paid, according to Moody’s RMS, due to the higher value of those policies. But federal coverage rates are falling, with a 5 percent decline nationwide since 2021 “We’re seeing a lot of cancellations over the last two years,” said Saleh.

Among Palm Springs’ nearly 24,000 households, just 167 were covered by federal flood insurance as of July 31, according to FEMA data. In the Northern California coastal town of Capitola, which saw its wharf wash away and homes flood last winter, only 66 of its 4,656 households have federal flood insurance.

Michael Soller, a deputy commissioner at the California Department of Insurance, said in an email that the state “has been working to increase consumers’ awareness of flood insurance protection gaps.”

Flood maps don’t reflect today’s climate risks.

FEMA taps historical, meteorological and topographic data to determine the likelihood of flooding from waterways as well as from storm-driven waves in coastal areas.

But the accelerating pace of climate change has outstripped those assumptions. That’s particularly true in California, which has swung between extremes of drought and deluge over the past decade. A tropical storm hitting California in the dead of a hot and dry summer probably was not on FEMA’s flood-probability bingo card.

“We’ve seen all over the country that the FEMA flood maps aren’t necessarily the best predictor of where flooding occurs,” said Kristina Hill, an associate professor at the University of California at Berkeley who studies sea-level rise and other climate impacts on urban hydrology. “So, what we’re seeing in California is that it’s not necessarily the areas designated as flood vulnerable that are the most flood vulnerable.”

During periods of drought, for instance, soil becomes compacted and less able to absorb water from heavy rains. The same is true for land stripped of vegetation by California’s growing wildfires. When it does rain, storms are more intense and frequent. Between December 2022 and March 2023, a dozen moisture-laden atmospheric rivers rolled into the state. Such torrential and sustained downpours can trigger flash flooding far from any waterway, overwhelming storm drains and other 20th-century infrastructure built for a climate that no longer exists. That also can cause water tables to rise, triggering further flooding as groundwater invades homes from below.

More rain means more snow in California’s mountains — 60 feet of snow fell on some ranges this past winter — posing flood threats when the snowpack melts amid rising temperatures. In the state’s Central Valley this year, meltwater and rainfall filled the long-drained Tulare Lake basin, submerging nearly 180 square miles of farmland.

“The flood maps are being updated with better modeling, but they’re not yet being updated for things like sea-level rise, groundwater rise near coasts and more intense rainfall,” said Hill.

Saleh noted that some flood maps are 15 years old and so don’t account for subsequent urbanization that exacerbates flooding as open space is paved over.

Get insured.

You can check if your home is in a government-designated flood zone by entering your address on FEMA’s website. Any homeowner can purchase federal flood insurance as long as their community participates in FEMA’s National Flood Insurance Program. The agency lists those communities on its website. You must purchase a federal policy through an insurance broker and the site lists providers by state. Renters can also obtain flood insurance to cover the loss of personal possessions. “FEMA recommends that everyone purchase flood insurance regardless of their flood zone,” the agency states.

Annual flood insurance premiums run about $900. Be forewarned, though, that federal flood insurance only takes effect 30 days after purchase and caps payouts at $250,000 for damage to your home and $100,000 for its contents. That doesn’t go far in a state like California, where the median home price nears $800,000 and exceeds $1 million in many cities. If you live in such a high-cost state, you’ll want to consider private flood insurance that offers higher coverage levels.

“Homeowners really need to consider the financial implications of what could happen if their property floods and they have to pay out of pocket,” said Saleh.