Heat domes are basically strengthening upper-level ridges of high air pressure that act like a lid on the atmosphere, suppressing widespread thunderstorm development while allowing surface temperatures to climb.
More than 230 million Americans are under the threat of extreme heat, with temperatures soaring into the 90s and the lower 100s. More than 20 states are expected to experience triple-digit heat heading into the Fourth of July holiday, including Texas, particularly in the Panhandle and West Texas.
While Central Texas will remain hot and mostly dry through the weekend, reaching the 100-degree mark may not be in the cards, except for parts of West Texas. Most forecast models keep afternoon highs at 97 or 98 degrees, just shy of the triple digits. The one exception is the Global Forecast System model, which continues to project highs between 100 and 102 degrees in Austin.
No widespread rainfall is expected over the holiday weekend, but we do have a slight chance of a few sea breeze showers on Thursday and Friday mornings, east of the Interstate 35 corridor.
July is typically dominated by strong systems of high atmospheric pressure over Texas, bringing the classic combination of intense summer heat and mostly dry weather. While most days are hot and sunny, the warm, humid air can still fuel an isolated afternoon thunderstorm capable of producing a quick burst of heavy rainfall.
Temperatures climb steadily throughout the month, with average highs increasing from 95 degrees on July 1 to 99 degrees, and morning lows ranging from 74 to 76 degrees through July 31. According to the National Weather Service, Central Texas typically experiences between 10 and 20 days each July with daytime highs reaching 100 degrees or higher, especially across the urban corridor and the Edwards Plateau.
Rainfall, however, is becoming much harder to come by. Most of Central Texas averages between 1 and 3 inches of rain during July, with Austin typically receiving 1.96 inches. That makes July the second-driest month of the year, trailing only February, which averages 1.89 inches of rainfall.
The forecast for the first half of July points to wetter weather than normal, which is reflected in the Climate Prediction Center’s six- to 10-day and eight- to 14-day outlooks. However, the outlook for the month favors below-normal rainfall. That suggests the early opportunities for rain may give way to a hotter, drier weather pattern later in the month as the heat dome strengthens and becomes more established over the Lone Star State.
In its eight- to 14-day temperature outlook, the Climate Prediction Center gives Austin a 48% chance of having above-normal temperatures through July 14, but almost equal chances of having below-normal or near-normal rainfall.