After a sweltering and parched week across much of Houston, a shift in the atmosphere is gearing up to bring heavy rainfall Friday, raising concerns for flash flooding in several parts of Southeast Texas, especially south of Interstate 10.
By Friday morning, atmospheric moisture levels — technically called precipitable water — are projected to rise above 2 inches, a signal that torrential rain could occur in a short span of time. For context, precipitable water reflects the amount of liquid water that could fall if all the water vapor from the surface up to the top of the atmosphere were condensed. Values above 2 inches often point to flood-risk conditions during thunderstorms.
This moisture surge is being driven by a tropical disturbance first identified late Tuesday by the National Hurricane Center, just off the Florida Atlantic coast. That system has since moved steadily west across the Gulf of Mexico, echoing the path of a similar system that recently unleashed downpours from Florida to Louisiana.
Now, as this tropical wave drifts closer to Texas, the National Weather Service’s Weather Prediction Center has marked a Level 1 out of 4 flooding risk for Houston, Galveston, and Beaumont. That corresponds to about a 5% chance of localized flash flooding, primarily in low-lying and flood-prone zones. Morning hours are expected to stay relatively dry as the storms need daytime heating to intensify — meaning commuters before noon might dodge the worst of it.
Rainfall projections through Sunday morning show totals around 1 inch (25 mm) for Southeast Texas, with the heaviest rainfall likely to fall south of I-10, while areas north of Houston may see lighter totals. Afternoon travel, especially on Friday, could become challenging as intense rainfall causes brief urban flooding.
Although evening skies are expected to clear somewhat, it’s wise to keep an umbrella handy. Rain chances dip after sunset as the sun’s heat fades, reducing the fuel thunderstorms need to develop.
Moving into Saturday, the pattern looks familiar: Dry mornings, followed by scattered storms and heavy rain in the afternoon. Places like Lake Jackson and Galveston could wake up to some early rain showers, but the main storm activity is expected later in the day. The flood threat will linger into Saturday night, though conditions should improve by Sunday as temperatures rise again.
While a full dry-out isn’t expected to start the new week, the chance for rain significantly decreases. Expect temperatures to climb into the upper 90s Fahrenheit (around 36°C) by Monday, with Sunday’s highs also reaching the mid-90s (around 35°C).
This current tropical disturbance offers a timely reminder of how quickly tropical systems can evolve. These start as tropical waves, which are essentially troughs of low atmospheric pressure drifting from east to west. As they strengthen and begin to rotate, they may become tropical depressions with sustained winds below 39 mph. Once winds cross that threshold, the system becomes a named tropical storm.
Should conditions remain favorable — like warm sea-surface temperatures and low wind shear — these storms can strengthen further. At 74 mph, the system becomes a hurricane, with the added risk of coastal storm surge posing a life-threatening danger to low-elevation communities.
Houston, Southeast Texas, and especially coastal zones like Galveston, will need to stay alert this Friday and Saturday as the wet weather returns in force.
