OKLAHOMA CITY (AP) — Forecasters warned of another day of heightened risk of dangerous tornadoes in the Midwest on Saturday and told people in South Texas they could experience triple-digit temperatures — and that's with four weeks to go before summer starts.

The weather service in Oklahoma compared the day to " a gasoline-soaked brush pile." Forecasters aren't certain storms will form, but any that do could explode with large hail, dangerous winds and tornadoes.

"There's a small chance most of the matches are duds and we only see a few storms today. Still, that's not a match I would want to play with. It only takes one storm to be impactful," the National Weather Service in Norman, Oklahoma, wrote on Facebook.

Excessive heat, especially for May, is the danger in South Texas, where the heat index is forecast to approach near 120 degrees F (49 degrees C) during the weekend. The region is on the north end of a heat dome that stretches from Mexico to South America, National Weather Service meteorologist Zack Taylor said.

Sunday looks like the hottest day with record-setting highs for late May forecast for Austin, Brownsville, Dallas and San Antonio, Taylor said.

The temperature was approaching 90 degrees F (32 degrees) and the heat index was 104 F (40 C) in Brownsville on the U.S./Mexico border by midmorning Saturday, according to the National Weather Service.

Red Flag fire warnings are also in place in west Texas, all of New Mexico and parts of Oklahoma, Arizona and Colorado, where very low humidity of below 10%, wind gusts of up to 60 mph (97 kph) combine with the hot temperatures.

"We've got very dry air, warm temperatures and strong winds creating a high fire danger over a wide area ... that can lead to rapidly spreading or uncontrollable fires," Taylor said.

Meanwhile, several inches of snow fell Friday into early Saturday in Rolla, North Dakota, about 10 miles (16 kilometers) from the Canadian border.

April and May have been a busy month for tornadoes, especially in the Midwest. Climate change is heightening the severity of storms around the world.

April had the country's second-highest number of tornadoes on record. And in 2024, the U.S. is already 25% ahead of the average number of twisters, according to the Storm Prediction Center in Norman, Oklahoma.

Iowa has been the hardest hit so far this week. A deadly twister devastated Greenfield. And other storms brought flooding and wind damage elsewhere in the state.

The storm system causing the severe weather is expected to move east as the Memorial Day weekend continues, bringing rain that could delay the Indianapolis 500 auto race Sunday in Indiana and more severe storms in Illinois, Indiana, Missouri and Kentucky.

The risk of severe weather moves into North Carolina and Virginia on Monday, forecasters said.