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Tuesday, June 1, 2021 at 8:55 AM Issued by: Mike Cooperstein  

Spring and Summer Avalanche Safety

Avalanches are possible any time you find snow on steep slopes in Colorado. Although accidents are less likely in the summer, there have been fatal accidents every month of the year. Below is some general avalanche safety advice for the spring and summer. Our next scheduled update is November 1, 2021. We will continue to monitor snowpack and weather conditions through the summer, and will issue updates if we anticipate unusually dangerous avalanche conditions before then.


You can get current weather forecasts from the National Weather Service. Our Computer Model Forecasts update four times a day and will run through the summer. If you are going into the Colorado high country, use our Weather Stations page to check current conditions.

Avalanche and Snowpack Discussion

Avalanches are possible in the mountains of Colorado whenever you find snow on a steep slope. In general, you should consider the consequences of being caught in an avalanche before you cross any steep, snow-covered slope, but below are some avalanche problems you may encounter over the summer. We will update the Field Report and Avalanche Observations as information comes in, so please send us your observations.

Storm Slabs, Wind Slabs, and Loose Dry Avalanches

Most avalanches happen during or right after a snowstorm. Later in the spring and throughout the summer, snowstorms are less likely. However, every time new snow falls and the wind drifts it through the terrain, these avalanches are possible. It is easier to trigger avalanches when new snow falls on hard, icy surfaces, so a summer snowstorm can produce many small avalanches if it falls onto old snow. Even small avalanches are dangerous if they push you off a cliff, or into rocks, trees, or a gully. The best way to manage these avalanches in the summer is to get a current weather forecast, recognize when there is enough new snow to produce storm avalanches, and select terrain that minimizes your exposure to the risk. Avoid areas where there was old snow under the recent snow, wind pillows along ridgelines, and cross-loaded features like rock outcrops and subridges.

Wet Slab and Loose Wet Avalanches

As the snow heats up and begins to melt, water moving through the snowpack can produce avalanches. Watch the overnight low temperatures at high-elevation weather stations, but remember that air temperature, cloud cover, and wind all affect how the snow freezes each night. Regardless of what wet avalanche you are worried about, remember to stay off and out from under steep snow-covered slopes when you start to sink into the wet snow more than about 6 inches. The most common wet avalanches are loose, sluff or point-release avalanches. These are most dangerous if they push you off a cliff, or into rocks, trees, or a gully. Travel when the snow surface is colder and stronger. Plan your trips to avoid crossing on or under very steep slopes in the afternoon. Move to colder, shadier slopes once the snow surface turns slushy. Avoid steep, sun-lit slopes above terrain traps, cliffs areas and long sustained steep pitches

Wet Slab avalanches are more dangerous. These often occur when melt flow of liquid melt water weakens the bond between the slab and the surface below (snow or ground). The snow conditions that produce Wet Slab avalanches last longest on high-elevation, northerly slopes as we move into summer. Look at the old snow layers to see if they are still dry or turning to coarse springtime snow. In many cases, snow conditions are poor when Wet Slabs are a significant problem. Most people leave the mountains or find places with firmer, less slushy snow and away from the slopes where Wet Slabs are a problem. Avoid terrain where and when you suspect Wet Slab avalanches. Give yourself a wide safety buffer to handle the uncertainty

Cornice Fall

Throughout the winter, strong winds build large overhanging snow features along ridgelines. These cornices can break off at any time of year, but periods of significant temperature warm-up during the spring are times to be particularly aware. Cornices can never be trusted and avoiding them is necessary for safe backcountry travel. Stay well back from ridgeline areas with cornices. Avoid areas underneath cornices. If your route goes under one, use a similar approach as Wet Slab avalanches, look for a good overnight freeze, and try to get past them early in the day. Remember that the sun may hit them earlier than it hits the slopes below them.

Thanks for another great season, and we will see you again in Fall 2021! Have a safe and enjoyable summer!


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Avalanche Observations
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Field Reports
Report Date Observer Snowpack Obs Avalanches Media

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Weather Observations
Station Date Time Temperature Relative Humidity Wind Speed Wind Direction Max Gust 24 Hr Snow
Bottle Peak Sat Sep 25 11:00 AM 50 29 20 275 23 -
Berthoud Pass Sat Sep 25 10:00 AM 48 28 4 311 17 -
Kendall Mt Sat Sep 25 11:00 AM 43 37 - - - -
Loveland Pass Sat Sep 25 11:00 AM 49 25 8 231 18 -
Molas Pass Sat Sep 25 11:00 AM 58 26 5 179 12 -
Putney Sat Sep 25 11:00 AM 52 28 7 231 14 -
Swamp Angel Sat Sep 25 11:00 AM 59 21 4 300 13 -
Vail Pass - Cdot Yard Sat Sep 25 11:00 AM 53 28 3 350 12 -
Wolf Creek Pass Sat Sep 25 11:00 AM 48 37 9 184 17 -
Hayden Pass Sat Sep 25 11:00 AM 50 - - - - -
Storm Peak Observatory Sat Sep 25 10:55 AM 51 - 10 225 15 -
Taylor Park Sat Sep 25 9:57 AM 51 34 4 67 6 -

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