The remnants of Hurricane Polo put much of southern and western Colorado under a Flood Watch through Thursday, and by Tuesday evening the first life-threatening flash flood warnings had landed on the burn scar the forecasters named that morning. Here is what a Colorado flood watch means above treeline, and what to change in your pack before you go.
At 11:59 on Tuesday morning, the National Weather Service office in Pueblo issued a Flood Watch and named the Aspen Acres burn area inside it. At 5:01 that evening the same office issued a Flash Flood Warning for the Middle Aspen Acres Burn Scar, naming Beulah and San Isabel. At 5:46 it issued a second one for the Southern Aspen Acres Burn Scar, with four words that do not appear in a watch: “Flash flooding is already occurring.”
Six hours from forecast to flood. That is the speed this hazard moves at, and it is the reason the rest of this week deserves more attention than a rain forecast usually gets.
Eight days ago, Polo was a Category 5 hurricane in the eastern Pacific with sustained winds near 180 mph. What is left of it is now a grey ceiling over southern Colorado, and the watch it triggered does something flood watches rarely do. It reaches the alpine.
Flood watches usually read like a valley problem: creeks, low-water crossings, the road beside the river. Read the zone names on this one and you find Pikes Peak above 11,000 feet, the Northern and Southern Sangre de Cristo Mountains above 11,000 feet, the Wet Mountains above 10,000, and the eastern San Juans above 10,000. The Sangre de Cristo zones alone cover the alpine terrain around the Crestones, Kit Carson, Humboldt and the Blanca group, which is where a fair number of people were planning to be this week.
What the Colorado flood watch actually says
Three NWS offices have parts of Colorado under a Flood Watch as of Tuesday afternoon, and all three name the same storm.
NWS Pueblo issued at 11:59 a.m. MDT Tuesday, running until noon Thursday, covering the Southeast Mountains, the Wet Mountain Valley, eastern Fremont County and the southeast plains. Its wording is blunt: “Flash flooding caused by excessive rainfall continues to be possible.” The cause, in the office’s own words, is “periods of heavy rainfall associated with a remnant tropical storm system.”
NWS Grand Junction issued at 11:22 a.m., running until 6 a.m. Thursday, covering the Northwest and Southwest San Juan Mountains and the San Juan River Basin. That office names Polo outright and spells out where the water goes: “Flooding will be possible over burn scars, at low-water crossings, and along creeks, streams, washes, arroyos and other flood-prone locations. Creeks and streams may rise out of their banks. Unpaved roads could become muddy and impassable.”
If you are camped somewhere Wednesday night, read that office’s last line twice: rainfall is expected to end late Wednesday, but “rivers may rise out of their banks overnight Wednesday even after rainfall has ended.”
NWS Denver issued at 2:05 p.m., covering far southeastern Elbert and southern Lincoln counties from midnight Tuesday through Thursday morning, with 1 to 2.5 inches of rain expected and locally higher amounts possible.
The air feeding all of this is genuinely strange. A weather balloon launched Monday evening by the NWS office in El Paso found roughly 250 percent of the normal moisture for the date, above the record for that day, and the Albuquerque office warned of “a near-record to record surge of moisture.”
Conditions change faster than trip plans do.
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Why this one reaches above treeline
Alpine terrain is close to the least absorbent ground in Colorado. Bare rock, talus, thin soil, no canopy to slow anything down. Rain that falls at 12,000 feet does not soak in. It finds the nearest channel and moves.
Every 14er route has channels. The gully you scramble, the drainage the trail crosses at 11,400, the apron of scree below a couloir: those are all watercourses that happen to be dry most of the time. Being high up does not protect you from a flash flood. Being out of the channel does.
That is also why the elevation bands in these watches are worth reading carefully rather than skimming for your county. The watch zones split the Sangre de Cristos at 11,000 feet and the Wet Mountains at 10,000 feet because the forecasters are describing two different hazards on the same mountain. If you are not used to reading a forecast that way, our guide on how to read a mountain weather forecast before your hike walks through the zones and what they actually mean.
The burn scars are the part to take seriously
NWS Pueblo named the Aspen Acres burn area in its watch text Tuesday morning. Grand Junction flagged burn scars generally. Both warnings that followed were burn-scar warnings.
Ground that burned this summer has lost the plants and the soil structure that used to absorb rainfall, so water runs across the surface instead of into it, gathering speed and debris on the way down. Both of Tuesday’s warnings describe debris flow, which the weather service defines as rock, mud, vegetation and other loose materials moving together down a drainage. The 5:01 warning named North Creek, Middle Creek and Squirrel Creek. The 5:46 warning named Middle St. Charles, Muddy Creek and Upper Greenhorn Creek. That is what comes down the channel, which is why standing near one to watch it is a worse idea than it looks.
On August 16, the weather service estimated that 1 to 1.5 inches of rain fell on Beulah over about an hour and a half. An 80-year-old man standing outside near Highway 78 and Central Avenue was swept away and carried roughly two miles downstream. Beulah fire personnel tried to reach him and could not.
An inch and a half. On burned ground, that was enough.
Tuesday’s 5:01 warning reported up to an inch already fallen on the Middle Aspen Acres scar, with up to another inch possible at a rate of half an inch an hour.
The Aspen Acres Fire Area Closure on the San Carlos Ranger District runs through December 31, so most of that ground is off limits anyway. The hazard worth planning around is the drainage downstream of a scar, which is usually open and usually looks fine.
Rain below, snow above 12,000 feet
The same storm is doing two things at once. Below about 12,000 feet it is rain, and a lot of it. Above that, several inches of snow are possible on the highest peaks.
Forecasters put the most likely outcome at three to six inches on the highest terrain through Thursday morning, with a roughly 10 percent chance of six to eight inches in southwest Colorado and 12 inches or more in a small part of the southern Collegiate Peaks near Salida.
So the first real traction-and-headlamp day of the season is arriving in the same 48 hours as the flood risk, which is a lot to absorb if you have been hiking in summer kit since June.
What to do between now and Thursday
- Read the elevation band, not the county. A watch that covers your trailhead at 9,000 feet may say something different about the ridge at 12,500. Check both.
- Treat every gully as a drainage. Do not camp in one, do not shelter in one, do not linger in one to wait out rain.
- Stay out of burn-scar drainages entirely, including the ones that look dry and open.
- Never drive or walk through water over a road. Six inches of moving water can knock an adult off their feet, and 12 inches will carry away most cars.
- Repack for the season. Waterproof shell, traction, a headlamp with fresh batteries, warm layers you can actually hike in, and a way to call for help where there is no cell signal.
- Know the difference between the two words. A watch means the setup is there. A warning means it is happening. Tuesday’s warnings told people to “move away and to higher ground immediately,” and one added a line worth carrying into the next two nights: “be especially cautious at night when it is harder to recognize the dangers of flooding.”
Repacking for the shoulder season?
Grab my free 14er gear checklist. It is the list I actually pack from, and it covers the layers, traction and light you need once the weather turns.
If you want to check a specific peak rather than a region, our Colorado 14ers weather forecasts page pulls the mountain-point forecast for each one. And if the flash-flood mechanics here are new to you, what the Colorado monsoon is and why it matters covers the same physics in the season most Coloradans learn it.
Colorado’s water year ends Wednesday at midnight, after the driest and hottest twelve months the state has on record. This is the wettest week it has had all year, and it arrives about 48 hours too late to change the number. The rain is welcome. Just do not be standing in a gully when it gets here.
Featured photo: The Next Summit / Alex Derr, a file photo from 2022, not from this storm. Watch and warning text quoted directly from the National Weather Service active alerts feed (NWS Pueblo, NWS Grand Junction and NWS Denver), read at 5:56 p.m. MDT on September 29, 2026. Additional reporting from the Kiowa County Press, the Denver Gazette and CBS Colorado. Warnings expire and new ones are issued; for what is live right now, check weather.gov before you go. TNS members get our conditions briefings first; membership details are here.
