Status: ACTIVE — extended. The National Weather Service in Fort Worth, Texas has extended a Flash Flood Warning for central Grayson County, in effect until 9:30 PM CDT on September 20, 2026. This is a live snapshot as of 8:04 PM CDT — conditions change fast. Always verify with the National Weather Service for your specific county or ZIP code.
Flash flooding is already occurring in the Denison area, per emergency management — and additional flash flooding is imminent or occurring from Sherman to Southmayd. Flooded roadways and water entering structures are the exact interior flooding jobs restoration teams see most after extended flash-flood warnings.
Grayson County, Texas — Flash Flood Warning (Extended)
The warning was extended by NWS Fort Worth, Texas at 7:35 PM CDT and runs until 9:30 PM CDT (VTEC /O.EXT.KFWD.FF.W.0085). Certainty is Likely; urgency is Immediate. Flash flood detection is listed as Observed.
- Hazard: Flash flooding caused by thunderstorms.
- Source: Emergency management reported.
- Observed at 7:35 PM CDT: multiple flooded roads in and around the Denison area. Flash flooding is already occurring in this area. Additional instances of flash flooding are imminent or occurring in the Sherman to Southmayd areas as well.
- Impact: Flash flooding of small creeks and streams, urban areas, highways, streets and underpasses, as well as other poor drainage and low-lying areas.
Some locations that will experience flash flooding include: Sherman, Denison, Pottsboro, Knollwood, Randell Lake, Eisenhower State Park, Southmayd, Boddie, and Carpenters Bluff.
The NWS instruction: Turn around, don’t drown when encountering flooded roads. Be especially cautious at night, when it is harder to recognize the dangers of flooding.
NWS office page: weather.gov/fwd (NWS Fort Worth). Alert source: the NWS Active Alerts feed via api.weather.gov.
Stay safe tonight
Most flood deaths occur in vehicles. Never drive through flooded roadways — water as shallow as six inches can sweep a person off their feet, and twelve inches can carry away a car. At night, flooded roads are nearly invisible: a road that looks passable may be washed out underneath.
If water enters your home: stay out of standing water where electricity may be present. Avoid the basement until water recedes and power is confirmed off. Photograph everything before cleanup — documentation matters for insurance. Then call a local restoration contractor — water left sitting starts a second wave of damage within a day.
If you are in the Denison, Sherman, or Southmayd areas right now: avoid creeks, streams, underpasses, and low-lying drainage areas. Move to higher ground if water begins rising near your home.
What this means for restoration teams
An extended flash-flood warning with observed flooding in the Denison area and more expected across Sherman to Southmayd is the classic multi-address water-intrusion event. The NWS impact wording maps directly to the work: small creeks and streams overflowing into low-lying neighborhoods, urban flooding in streets and underpasses, and poor-drainage areas taking water.
- Damage categories to expect across central Grayson County: interior water intrusion through doorways and foundation seepage, saturated drywall and insulation on ground floors, sewage backup in low-lying areas, and vehicles damaged in flooded roadways and parking areas.
- The play: stage extraction and drying equipment now, pre-position dehumidifiers and air movers, and keep an on-call rotation through the night. Water standing in homes overnight drives secondary damage — get the first extraction call dispatched fast.
- First-call capture: address, water source (rising creek, street flooding, backed-up drain), which rooms and floor levels are affected, and whether sewage is involved. Photo-document everything before mitigation, moisture-map every affected room, and keep the homeowner’s payment responsibility clear in writing before work starts.
- Field discipline: mold risk follows within 24–48 hours on saturated materials. Treat any floodwater as potentially contaminated — especially where sewage backup is possible in low-lying areas.
FEMA & federal assistance
FEMA Helpline: 1-800-621-3362 (7 a.m.–10 p.m. local time, 7 days a week). You can also apply at DisasterAssistance.gov, through the FEMA app, or find recovery centers at fema.gov/drc.
Basic eligibility: U.S. citizenship or qualified immigration status, identity verification, proof of occupancy or ownership of the damaged home, and unmet needs not covered by insurance. Apply as soon as it’s safe to do so.
Looking ahead
The extended warning runs until 9:30 PM CDT. Small creeks and streams often crest after the rain stops — water levels in low-lying areas can keep rising even after the warning expires, so don’t assume the danger passes at 9:30.
Watch for additional rounds of thunderstorms overnight. If more warnings are issued for Grayson County, NWS Fort Worth will update the alert stream — check weather.gov for your ZIP before driving anywhere tonight.
Sources & how to verify
- NWS alert: api.weather.gov active alerts feed (urn:oid:2.49.0.1.840.0.7a4e058c9e6f2e4c107ebe9446aca8dfcfc29c0a.001.1), read 2026-09-20 ~8:02 PM CDT.
- Issuing office: NWS Fort Worth, Texas (weather.gov/fwd).
To verify for your own county or ZIP: go to weather.gov, enter your ZIP code, and read the active alerts banner at the top of your local forecast page.
This post is for informational purposes and is not an official weather warning. Always follow instructions from local authorities and the National Weather Service.
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