3 to 7 Inches Along I-35 This Week: What the Flood Risk Maps Actually Mean | Sunday Update

After two months of heat and drought, the pattern flips this week. Hurricane Polo's remnants feed an upper-level storm system that brings rain to nearly all of Texas — and flooding risk, especially along I-35 midweek. Special Sunday evening update, September 27, 2026.

POLO'S REMNANTS & THE UPPER LOW
The heat dome is gone. A big dip in the jet stream digs into the southwestern US Monday into Tuesday, then becomes a closed upper-level low over western Texas and New Mexico Tuesday through Friday.

Hurricane Polo's remnants will move out of Baja California into eastern New Mexico and western Texas, where that storm system absorbs them. That means deep moisture plus several days of upper-level lift. Not a hurricane in Texas — just its leftover moisture, carried by the jet stream.

SEVERE STORM POTENTIAL
No official SPC outlooks yet, but there's a low-end threat of isolated damaging wind gusts, and a tornado can't be ruled out. The most widespread issues will be heavy rain and plenty of cloud-to-ground lightning.

FLOOD RISK DAY BY DAY
Monday and Monday night: Level 2 of 4 — isolated to scattered flash flooding possible around El Paso, Van Horn and a sliver of the northwestern Panhandle.

Tuesday and Tuesday night: Level 3 of 4 (Moderate Risk) for the Panhandle, West Texas and the Borderland — El Paso, Lubbock, Amarillo, up through Dumas and Dalhart. Numerous instances of flooding possible, with some significant rapid-onset flooding. The eastern two-thirds sees only isolated storms Monday and most of Tuesday.

Wednesday and Wednesday night: Level 3 of 4 across Texoma and North Texas, southwest into the Big Country, Concho Valley and parts of the Hill Country. Level 2 covers South Central Texas, the Edwards Plateau, Permian Basin, Panhandle and parts of Northeast Texas. It's rare to see a Level 3 this far out.

Thursday and Thursday night: a Level 3 is already on the Day 5 outlook for DFW, Sherman, Waco, Killeen, the Hill Country, Austin and San Antonio, with Level 2 surrounding it across much of the rest of the eastern half. These outlooks will shift as the forecast is refined.

WHAT THESE MAPS ACTUALLY MEAN
A Level 3 does not automatically mean a catastrophic, high-end flood. I want to make that clear, because a lot of bright maps have been flying around social media today.

These are probability maps — the chance that rainfall exceeds flash flood guidance within 25 to 40 miles of you, meaning more rain than the soil can absorb. Level 2 is 15 to 40%. Level 3 is 40 to 70%.

By Thursday, soils will be more saturated from earlier rain, so it takes less new rain to cause flooding.

RAIN TOTALS
Through 7 PM Friday, nearly every spot in Texas should see rain this week. We need it. That's good news.

The heaviest axis sits along the I-35 corridor: 3 to 7 inches from Pearsall up through San Antonio, Austin, Killeen, Waco, Bryan-College Station, Fairfield, Corsicana, the DFW Metroplex, Gainesville and Sherman to Lake Texoma. Most of the eastern 75% of Texas sees 1 to 2 inches, locally more. The Big Bend mostly misses out.

Rate is what matters. 3 to 7 inches over two days means some flooded low spots on roads. 3 to 7 inches in three hours means rapid-onset flooding, because all that water has to go somewhere fast.

DAY-BY-DAY TIMING
Monday night: heavier rain reaches El Paso and far West Texas. Tuesday: the western third's day, with some strong storms and likely flash flood warnings. Late Tuesday into Wednesday: rain expands east into the Big Country, Northwest Texas, Texoma, North Texas, Central Texas and the Hill Country.

Wednesday night through Friday: the eastern half to two-thirds of Texas gets the highest rain chances. This is when storms could start training — moving repeatedly over the same areas like a train on the tracks — and that's when we could get too much rain.

WE'VE SEEN THIS SETUP BEFORE
Remnant Pacific hurricane moisture plus an upper-level storm system is a classic fall flooding setup. We saw it with Hurricane Patricia's moisture in 2015.

From flash drought and triple digits to a nearly statewide rain event — welcome to fall. Multiple updates each day this week. Turn around, don't drown.

CHAPTERS
0:00 The Pattern Flips
0:54 Polo's Remnants & the Upper Low
1:57 Severe Storm Potential
2:20 Monday's Flood Risk
2:52 Tuesday: Level 3 Out West
3:46 Wednesday: Level 3 North & Central
4:54 Thursday: Level 3 Along I-35
5:32 What These Maps Actually Mean
6:25 Rain Totals: 3-7 Inches
9:17 Day-by-Day Timing
10:55 We've Seen This Setup Before

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