Destructive West Texas wildfires that forced hundreds of evacuations expanded by almost 20% as the prospect for violent weather disrupted airline travel and threatened urban centers such as Houston with flooding, tornadoes and blackouts.

The blazes that erupted late last week west of the Dallas metropolitan area had grown to more than 63,000 acres (25,500 hectares) by Monday afternoon. While the fire threat remains high across West Texas, central and eastern areas—including some areas scorched last week—are facing severe thunderstorms and flooding rains.

The collection of plagues, coming as firefighters battle wildfires in the state’s arid western plains, has been spawned by a clash of weather systems rolling across the Rocky Mountains and Gulf of Mexico. Houston, Dallas, Austin and Arlington are bracing for heavy rain, slashing winds and dangerous hail through Tuesday morning, according to the Storm Prediction Center.

“A couple of strong tornadoes are possible,” forecasters Chris Broyles and Brian Squitieri said in their outlook.

Meanwhile, the Midcontinent Independent System Operator that operates the central U. S. power grid stretching from the Great Lakes to the Gulf Coast, asked generators and transmission owners to defer any maintenance ahead of the arrival of severe weather in eastern Texas around 6 p.m.

The most severe weather is expected to peak Tuesday afternoon, MISO said in a notice. More than 400 head of cattle and other livestock have perished and 110 displaced by fire are being housed in temporary shelters, according to the Texas Animal Health Commission.

At least 433 flights were canceled at Dallas’s two major airports, according to FlightAware, an airline-tracking service.

The storms are being propelled “a classic spring severe weather setup” as powerful storm sweeping over the Rocky Mountains taps into a deep reservoir of moist warm air coming out of the Gulf of Mexico, said Zack Taylor, a senior branch forecaster at the U.S. Weather Prediction Center. In addition to the wind and thunderstorm risk, eastern Texas, as well as parts of Louisiana and Arkansas, will face the potential for flash flooding.

“This time of year we have plenty of good ingredients for severe weather,” Taylor said. The threat for severe thunderstorms and heavy rains shift east into Alabama and Mississippi on Tuesday.

Critical fire conditions reach across more than 40,517 square miles of central Texas, including San Angelo, as warm, dry winds gust across the region to the west of where the Dallas wildfires rage, the U.S. Storm Prediction Center said. There are a cluster of fires near Cisco, Texas, according to the Texas Wildfire Incident Response System.

Warm winds and crackling dry air can combine to create dangerous situations where fires can rapidly spread, the agency said. Nearly 375,000 people live in the area affected by Monday’s warning. A larger region covering almost all of west Texas is under a red flag fire warning.