Houston, San Antonio and Austin at risk of flash flooding Wednesday

Much of south Texas, including Houston, was bracing for heavy rain that could lead to flash flooding Wednesday.

Southeast Texas will face a moderate risk of excessive rainfall Wednesday, and the National Weather Service predicted that some areas will get more than 5 inches of rain.

"Residents and visitors throughout this region are advised to pay close attention to the forecast, especially if you live within a flood-prone region," the weather service said Tuesday.

Parts of the Houston metropolitan area were already under flash flood warning Tuesday afternoon.

Parts of the Central Plains can also expect thunderstorms Wednesday, according to AccuWeather.

In the western U.S., cities in California and Oregon are experiencing cooler than average temperatures this week, before things start to heat up this weekend.

Huge swath of Texas will get heavy rain

Several of the Lone Star State's biggest cities, including Houston, San Antonio, Corpus Christi and Austin, are expected to get pounded by rain Wednesday and Thursday, AccuWeather forecasters said.

The outlet predicted some localized areas could get up to 8-12 inches of rain; San Antonio and the Texas Hill Country will possibly be inundated with the most precipitation.

Thunderstorms possible in Central Plains

Rocky Mountain cities such as Denver and Cheyenne, Wyoming, will have a moderate risk of thunderstorms Wednesday, AccuWeather reported.

The National Weather Service said Tuesday that it predicts about 1-3 inches of rainfall in the region through Thursday.

The region is at some risk of damaging wind and hail, AccuWeather forecasters said, and there's also a low risk of flooding and tornadoes.

Cooler temps continue along West Coast

Major cities including Los Angeles, San Francisco, Portland and farther inland such as Las Vegas, Boise and Salt Lake City are feeling temperatures that are 5-15 degrees cooler than average for this time of year, AccuWeather reported.

But as soon as Thursday, a change in the jet stream will lead the same region to experience unseasonably warm temperatures.

US weather watches and warnings

National weather radar

This article originally appeared on USA TODAY: Today's weather forecast includes heavy rain in southeast Texas