Memorial Day Weekend Brings Thunderstorms, Flash Flood Risks and Dangerous Heat Across Parts of the United States

A stormy holiday taking shape across the eastern United States

For millions of Americans, Memorial Day weekend is ending under restless skies.

Families heading to beaches, backyard cookouts, lakes, and cemeteries for holiday observances across the eastern half of the United States may find themselves dodging thunderstorms as a slow-moving weather system spreads rain and heavy downpours across a huge stretch of the country.

The air across much of the South and East feels thick with moisture. Clouds bubble up quickly through the afternoon. In some places, the sound of thunder is already rolling in before dinner.

Forecasters say showers and thunderstorms are expected from the Lower Mississippi Valley through the Southeast, OH Valley, Mid-Atlantic, and Northeast as low pressure interacts with warm, humid air stalled along a slow-moving front.

The wet pattern is expected to continue through Memorial Day on May 25.

Some storms could become severe.

More than 10 million people are under a level two out of five severe thunderstorm risk, including parts of Texas, USA, Florida, USA, Georgia, USA, Nebraska, USA, South Dakota, USA, Minnesota, USA, and New Mexico, USA.

The storms may bring damaging wind, lightning, torrential rain, and localized flooding.

A calm morning may not stay calm for long.

Flash flooding threat grows from Louisiana to the Carolinas

The heaviest rain is expected across parts of the Gulf Coast and Southeast, where repeated storms could dump large amounts of rain over the same areas.

Forecasters say the greatest flash flooding threat stretches from southeastern Louisiana, USA through Tennessee, USA and into the Carolinas.

Water levels are already beginning to rise in some flood-prone communities.

Roads in parts of southeast Texas turned waterlogged over the weekend after flash flooding was reported in the Houston, TX and Galveston, TX forecast region.

On May 24, nearly 17 million people from Texas to West Virginia, USA were under flood watches.

The rain has been relentless in some Gulf Coast communities.

The National Weather Service office in New Orleans, LA said Gulfport, MS received 7.19 inches of rain over three days. Houma, LA recorded 4.09 inches, while New Orleans, LA picked up slightly more than 3 inches.

Storm drains overflowed in some neighborhoods. Water collected along highways and low-lying streets. In places where the rain fell hardest, visibility dropped sharply as sheets of water swept across roadways.

The rain is arriving in areas desperately needing moisture after months of worsening drought. But forecasters warn that too much rain too quickly creates an entirely different danger.

Dry ground cracks one week. Flash flooding the next.

Meteorologists tracking a stubborn weather pattern

Weather experts say the current setup may allow rounds of storms to repeatedly redevelop over similar areas during the coming days.

Meteorologist Alan Gerard said an upper-air pattern known as an omega block appears to be developing across the country. The pattern places strong high pressure over parts of the central United States while stormier conditions remain active farther south.

That combination may help generate repeated waves of thunderstorms fueled by extremely moist air.

Gerard warned the setup could produce “torrential downpours" in some areas.

The broader backdrop remains concerning for meteorologists monitoring drought conditions nationwide.

According to data released by the U.S. Drought Monitor on May 21, the percentage of the country experiencing severe or worse drought has doubled during the last three months, increasing from 22% to 44%.

The nation’s Drought Severity and Coverage Index has climbed to its highest level since 2012.

Western states stay hot and mostly dry

While storms soak much of the eastern United States, a very different weather story is unfolding farther west.

A broad area of high pressure is keeping much of the Western United States dry, sunny, and unusually warm for late May.

Desert areas of California, USA, Nevada, USA, and Arizona, USA are expected to see temperatures climb into the 100s during the early part of the week.

The heat is building across dry valleys and desert communities where the afternoon sun beats down without many clouds to offer relief.

In parts of California, the landscape already looks parched. Hillsides appear pale brown beneath the bright sky as early-season heat settles into the region.

The Pacific Northwest may see a brief break from the dry weather later in the holiday period. Forecasters say showers are possible in parts of the region, while the highest elevations of the Cascades could even pick up some snow.

Cold water dangers remain across Maine lakes

In Maine, USA, meteorologists are warning that one of the biggest holiday dangers may not come from storms at all.

The National Weather Service office in Gray warned that lakes and rivers across the region remain dangerously cold despite milder air temperatures.

Water temperatures across Sebago Lake and Lake Winnipesaukee are only in the mid-50s, with similar readings reported elsewhere across the region.

Officials warned that anyone falling into water colder than 60 degrees could quickly face hypothermia.

“Anyone on small boats, canoes, or kayaks should plan accordingly... and use extreme caution," the weather service said.

For many people spending the holiday outdoors, the weather will shift dramatically depending on where they are.

Blazing heat in the West. Flash flooding rain in the South. Thunderstorms rolling through the East while cold lake water waits quietly beneath calm-looking surfaces in the Northeast.