Alert archive / Montana / Flash Flood Warnings
Flash Flood Warnings in Montana, 2026
42 flash flood warnings in 2026. An alert counts here when it covered any part of the state, so the counties below add up to more than the state. The archive of flash flood warnings reaches back to 1986.
Flash Flood Warnings by county
Each county as a circle sized by its count in 2026. Tap one for its archive.
- Flash Flood Warnings
- 42
- Busiest month
- July20 flash flood warnings
- Busiest day
- June 28, 20268 flash flood warnings
Over time
By month
Warning verification
How often warnings here had a storm report inside them, and how much warning the reports had.
5 of 42 flash flood warnings covering Montana in 2026 had a flash flood report inside them; 10 of 18 flash flood reports fell inside a warning, on average 37 minutes after it went out.
Montana, 2026
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| Flash flood warnings | 42 | 5 | 88% | 18 | 56% | 37 min |
Each office's whole area, 2026
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| NWS Great Falls, MT: flash flood warnings | 8 | 1 | 88% | 2 | 50% | 1 min |
| NWS Missoula, MT: flash flood warnings | 5 | 0 | 100% | 6 | 0% | |
| NWS Billings, MT: flash flood warnings | 19 | 1 | 95% | 4 | 25% | 75 min |
| NWS Glasgow, MT: flash flood warnings | 16 | 3 | 81% | 9 | 89% | 37 min |
An office's figures cover every county it serves, including across state lines.
The year is still running; reports filed late and damage surveys can still change these figures.
Verified by the Iowa Environmental Mesonet's Cow, which matches each storm-based warning with the local storm reports inside its polygon while it was in force, within 15 km of its edge: a tornado warning counts as verified on a tornado report, a severe thunderstorm warning on hail of 1 inch or more, a gust of 58 mph or more, or wind damage, a flash flood warning on a flash flood report. The false alarm ratio is the share of warnings with no such report; "inside a warning" is the probability of detection, the share of reports that fell inside one; lead time runs from the warning's issue to each report inside it, counting zero for a report that came first. A warning with no report is not proof nothing happened: reports come from spotters, the public and damage surveys, and are thin where few people live.
The alerts
Every alert, in the order issued. Times are local, Mountain Time. Each opens its own page with the text, the map, the radar and the sounding.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 28, 6:13 PM MDT | Flash Flood Warning | TFX | Glacier | 114 min |
| May 29, 4:32 PM MDT | Flash Flood Warning | BYZ | Rosebud | 3 hr |
| Jun 20, 11:42 PM MDT | Flash Flood Warning | BYZ | Rosebud | 3 hr |
| Jun 22, 2:11 PM MDT | Flash Flood Warning | BYZ | Rosebud | 4 hr |
| Jun 27, 12:41 PM MDT | Flash Flood Warning | BYZ | Stillwater | 3 hr |
| Jun 27, 2:07 PM MDT | Flash Flood Warning | BYZ | Yellowstone | 3 hr |
| Jun 27, 2:28 PM MDT | Flash Flood Warning | BYZ | Rosebud | 3 hr |
| Jun 27, 3:02 PM MDT | Flash Flood Warning | BYZ | Big Horn | 3 hr |
| Jun 27, 4:59 PM MDT | Flash Flood Warning | GGW | Valley | 118 min |
| Jun 27, 6:13 PM MDT | Flash Flood Warning | GGW | Richland | 5 hr |
| Jun 27, 6:33 PM MDT | Flash Flood Warning | GGW | Garfield | 4 hr |
| Jun 27, 7:05 PM MDT | Flash Flood Warning | GGW | Roosevelt | 4 hr |
| Jun 27, 7:50 PM MDT | Flash Flood Warning | GGW | Richland, Roosevelt | 3 hr |
| Jun 27, 7:53 PM MDT | Flash Flood Warning | GGW | Dawson, Richland | 116 min |
| Jun 27, 8:19 PM MDT | Flash Flood Warning | GGW | Roosevelt, Sheridan | 3 hr |
| Jun 27, 8:30 PM MDT | Flash Flood Warning | GGW | Daniels | 3 hr |
| Jun 27, 9:32 PM MDT | Flash Flood Warning | GGW | Roosevelt | 3 hr |
| Jul 1, 2:51 PM MDT | Flash Flood Warning | TFX | Broadwater, Jefferson, Lewis and Clark | 109 min |
| Jul 2, 7:09 PM MDT | Flash Flood Warning | BYZ | Rosebud | 3 hr |
| Jul 3, 4:24 PM MDT | Flash Flood Warning | GGW | Valley | 5 hr |
| Jul 3, 5:00 PM MDT | Flash Flood Warning | GGW | Garfield | 3 hr |
| Jul 3, 5:12 PM MDT | Flash Flood Warning | GGW | Garfield | 3 hr |
| Jul 3, 5:18 PM MDT | Flash Flood Warning | GGW | Valley | 4 hr |
| Jul 3, 5:40 PM MDT | Flash Flood Warning | GGW | Valley | 3 hr |
| Jul 14, 7:24 PM MDT | Flash Flood Warning | TFX | Fergus | 3 hr |
| Jul 14, 8:29 PM MDT | Flash Flood Warning | TFX | Fergus | 3 hr |
| Jul 14, 9:33 PM MDT | Flash Flood Warning | GGW | Petroleum | 3 hr |
| Jul 15, 3:01 PM MDT | Flash Flood Warning | BYZ | Stillwater | 3 hr |
| Jul 16, 7:48 PM MDT | Flash Flood Warning | BYZ | Golden Valley, Musselshell | 3 hr |
| Jul 17, 2:16 PM MDT | Flash Flood Warning | BYZ | Park, Sweet Grass | 3 hr |
| Jul 17, 4:14 PM MDT | Flash Flood Warning | MSO | Granite | 2 hr |
| Jul 17, 4:15 PM MDT | Flash Flood Warning | MSO | Granite | 2 hr |
| Jul 17, 4:37 PM MDT | Flash Flood Warning | MSO | Granite | 2 hr |
| Jul 17, 5:09 PM MDT | Flash Flood Warning | MSO | Missoula, Powell | 93 min |
| Jul 17, 9:06 PM MDT | Flash Flood Warning | TFX | Broadwater, Lewis and Clark | 4 hr |
| Jul 22, 7:54 PM MDT | Flash Flood Warning | TFX | Broadwater, Lewis and Clark | 3 hr |
| Jul 30, 5:41 AM MDT | Flash Flood Warning | GGW | Garfield, Valley | 3 hr |
| Aug 14, 8:31 AM MDT | Flash Flood Warning | MSO | Ravalli | 3 hr |
| Sep 6, 9:51 PM MDT | Flash Flood Warning | TFX | Hill, Liberty | 3 hr |
| Sep 6, 10:04 PM MDT | Flash Flood Warning | TFX | Hill, Liberty | 3 hr |
| Sep 18, 6:02 PM MDT | Flash Flood Warning | BYZ | Golden Valley, Wheatland | 4 hr |
| Sep 18, 7:40 PM MDT | Flash Flood Warning | BYZ | Golden Valley, Sweet Grass | 2 hr |
By county
Every county with at least one alert. A county page lists each alert that covered it.
- Rosebud County5
- Valley County5
- Garfield County4
- Roosevelt County4
- Richland County3
- Broadwater County3
- Lewis and Clark County3
- Golden Valley County3
- Granite County3
- Stillwater County2
- Fergus County2
- Sweet Grass County2
- Hill County2
- Liberty County2
- Glacier County1
- Yellowstone County1
- Big Horn County1
- Dawson County1
- Sheridan County1
- Daniels County1
- Jefferson County1
- Petroleum County1
- Musselshell County1
- Park County1
- Missoula County1
- Powell County1
- Ravalli County1
- Wheatland County1
The busiest days
Days with the most alerts issued, by UTC date.
Nearby
Sources
National Weather Service watches, warnings, advisories and statements from the Iowa Environmental Mesonet's VTEC archive, which reconstructs tornado, severe thunderstorm, flash flood and marine warnings back to 1986 from the NWS text archive. Storm Prediction Center watches and mesoscale discussions from SPC's archive through the Mesonet. County centers from the US Census Bureau. Warning verification from the Mesonet's Cow. Rebuilt daily.