Southern Colorado’s late-October rainstorm ranks among most extreme in state records

The rain-soaking event from October 21-25 across the San Juan Mountains and San Luis Valley belongs on the short list of Colorado’s most extreme rainstorms ever recorded, according to Colorado Climate Center (CCC) State Climatologist Russ Schumacher.

In an analysis published Oct. 30 on the CCC blog, Schumacher wrote that the October 21-25 storm topped even the region’s notorious 1911 and 2025 fall floods by some measures, especially at lower and middle elevations.

“The meteorological setup for this event was slightly different from those past cases, which had a more direct influence from the remnant tropical cyclones,” Schumacher said. “The late-October event did have some influence from Tropical Storm Trudy, which formed and moved northward toward the west coast of Mexico in mid-October.”

During the 2026 event, heavy rain fell across southern Colorado and parts of New Mexico, Utah and Arizona over the five-day stretch.

Schumacher reported no fatalities or significant injuries as of the CCC’s publication, but said the storm caused extensive damage, including washed-out roads, damaged homes, water rescues and affected recreation areas.

Notable highlights:

• Up to 8 inches of precipitation fell over four days at high elevations, with widespread 4 to 6 inches at lower elevations.
• The San Luis Valley, which averages only 7 to 9 inches of precipitation a year, got roughly 2 to 4 inches in four days, more than four times its typical October total.
• Alamosa, Monte Vista and Del Norte recorded their wettest two-day periods on record, and Alamosa and Monte Vista their wettest three-day periods.
• Several areas of the San Luis Valley exceeded a 1,000-year rainfall event over the 48 hours ending the morning of Oct. 23, according to NOAA Atlas 14 estimates.
• A CoCoRaHS observer in South Fork measured 4.46 inches in two days and 5.64 inches over four days.
• The San Juan River at Pagosa Springs crested more than 2 feet higher than during last October’s flood.
• Roughly 884,000 acre-feet of water fell across Mineral, Hinsdale and Archuleta counties from Oct. 22-25, according to Assistant State Climatologist Peter Goble.
• Much of southwestern Colorado is now drought-free, after drought improvements of three to five categories in two months.
• Another storm was expected this weekend, with the greatest flood risk on Sunday, Nov. 1.

What caused it: a “firehose” of tropical moisture

The setup started with Tropical Storm Trudy, which formed in mid-October off Mexico’s west coast and dissipated without reaching the United States.

According to Schumacher, moisture from Trudy and elevated Pacific moisture linked to El Niño was drawn north by a strong trough approaching the West Coast, creating a sustained “firehose” of water vapor aimed at southern Colorado.

The pattern fits the region’s flood history too. Schumacher noted that many of southern Colorado’s biggest fall storms have involved remnants of eastern Pacific tropical systems.

The October 1911 “Sonora hurricane” produced the flood of record on the San Juan River, and two back-to-back tropical systems drove last October’s floods.

Remnants of Tropical Storm Polo also brought rain and flooding earlier this fall.

Where the rain fell

The heaviest totals centered on the San Juan Mountains in Colorado and New Mexico and the Abajo Mountains in southeastern Utah.

The San Luis Valley stood out. One of the driest places in the state took in more than four times its normal October precipitation in just four days.

How rare it was

To gauge how unusual the rainfall was, Schumacher compared estimated 48-hour totals ending the morning of Oct. 23 against NOAA Atlas 14 return periods, using the “most likely” values:

• Much of the region exceeded a 10-year event.
• Parts of Archuleta County and much of the San Luis Valley exceeded a 100-year event.
• Several areas of the San Luis Valley exceeded a 1,000-year event.

Ground observations backed up the gridded estimates.

In South Fork, a CoCoRaHS volunteer recorded 4.46 inches in two days, an amount with less than a 1-in-1,000 chance of occurring in a given year, then another 1.15 inches on Oct. 25, for a four-day total of 5.64 inches.

The Fun Valley Family Resort near South Fork was among the sites that saw significant damage. Pagosa Springs has now been hit by two major floods in two years.

Schumacher thanked the CoCoRaHS volunteers who documented both events, many of them recruited by the Pagosa Weather team.

How it compares to last October’s flood

This storm and the October 2025 event hit some of the same communities, but in different ways. According to Schumacher:

• The 2026 storm brought considerably more rain to the San Juan and Rio Grande watersheds, including 2 to 4 inches more in the San Luis Valley, Archuleta County and northern New Mexico.
• The 2025 storm produced more precipitation at the highest San Juan elevations and in La Plata County.
• Much of this year’s high-elevation precipitation fell as snow rather than rain.
• The San Juan River at Pagosa Springs crested more than 2 feet higher in 2026 than in 2025.

A new entry on Colorado’s list of extreme rainstorms

Schumacher compared the storm’s coverage of very rare rainfall amounts to the September 2013 Front Range floods, and wrote that the 2026 event had greater coverage of such amounts.

He argued the 2026 storm should join the list of Colorado’s most extreme rainstorms:

• The October 1911 Sonora hurricane
• The June 1921 storm that flooded Penrose and Pueblo
• The June 1965 storms in northern and southeastern Colorado
• The 1976 Big Thompson storm and flood
• The September 2013 Great Colorado Flood

From record drought to record flows

The 2026 storm capped a dramatic two-month reversal.

After a poor snow season and a hot, dry summer that made Water Year 2026 the warmest on record, much of southern Colorado has seen record-high precipitation since early September, according to the CCC.

• Much of southwestern Colorado is now drought-free on the U.S. Drought Monitor.
• Rivers that ran near record lows this summer are now near record highs for the fall.
• Navajo Reservoir, which was approaching record lows in early September, got a major boost.
• Lake Powell is no longer at a record low, though it remains close to that range.
• Granby Reservoir and Blue Mesa Reservoir saw little increase.

Schumacher cautioned that the recovery doesn’t undo the impacts of the earlier drought, and that Colorado still needs a good mountain snow season.

El Niño’s role and what’s next

Fall is the season when El Niño has its strongest link to precipitation in Colorado, typically making southern Colorado wetter, according to the CCC. This fall’s precipitation pattern closely matches that historical correlation.

El Niño years also tend to produce more eastern Pacific hurricanes (22 named storms and 12 hurricanes in 2026), which raises the odds of extreme rain events like this one.

Another potent storm is expected over the Halloween weekend, with the greatest flood risk on Nov. 1. Snow is forecast at higher elevations in Colorado.

The National Weather Service in Grand Junction issued a Winter Storm Watch in effect from Nov. 1 morning through noon Nov. 2 for the northwestern and southwestern San Juan Mountains, where heavy snow is possible above 10,000 feet with total snow accumulations between 10-15 inches with locally higher amounts.

A winter weather advisory is in effect from noon Sunday, Nov. 1 to 6 p.m., Monday, Nov. 2 for areas in the west-central mountains of Colorado. Snow is expected above 10, 000 feet, with total snow accumulations of between 5-10 inches for areas in the West Elk and Elk mountains near Aspen, in the Gore Range near Vail, in the western Sawatch, and in the Flat Top Mountains and on the Grand Mesa.

Looking further ahead, Schumacher noted that El Niño’s influence on Colorado weakens in midwinter, so a big snow season is possible, but not guaranteed.