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By Alan Smith, Meteorologist Posted 1 month ago June 21, 2024

Expert Tips: Avoiding Thunderstorms on Colorado 14ers

Colorado's 14,000-foot peaks (14ers) are popular objectives for hikers and peak-baggers. The above-treeline terrain on these peaks are subject to more extreme weather compared to surrounding lower terrain, including colder temperatures, stronger winds, and snow.

The most notable weather hazard during prime summer hiking season is lightning as thunderstorms are very common over these high peaks.

Fortunately, with proper planning and observation, you can minimize your risk of lightning while hiking a fourteener. 

What is a "14er"?

A "14er" refers to any peak with a summit above 14,000 feet. There are 58 such peaks in the state of Colorado, which is more than any other state in the U.S. Hiking or climbing these peaks makes for a popular objective in Colorado, as the challenge and beauty of these peaks have allured the outdoorsy types for decades. 

All fourteeners are challenging to some degree, given the elevation gain and lack of oxygen at such a high altitude. However, technical ability varies significantly with some peaks involving walk-ups on well-established hiking trails, while other peaks involve highly-exposed scrambles with route-finding over rocky terrain.

When is the Best Time of Year to Hike a Fourteener?

It depends somewhat on the specific peak and individual ability/experience on snow-covered terrain. However, the typical season for snow-free travel and milder temperatures is from July through September. This is by far the most popular season for hiking Fourteeners, and it also coincides with thunderstorm season.

How Common Are Thunderstorms on 14ers?

Thunderstorms are very common in the Colorado Rockies during the summer months, often developing on a near-daily basis for weeks on end during the peak season of July and August.

Most major mountain ranges in Colorado average 54-72 thunderstorm days per year, while portions of the San Juan Range as well as Pikes Peak average 72-81 thunderstorm days per year. Only the Gulf Coast and Florida see more thunderstorm days on average. 

In the Colorado Rockies, the combination of orographic lift and solar heating of mountain slopes at a more direct angle results in more frequent thunderstorms developing over the higher peaks, and also earlier in the day compared to surrounding valleys. 

Learn More → Key Ingredients for Mountain Thunderstorms

A major contributor to thunderstorm patterns in Colorado during the summer months is the North American Monsoon. This is a seasonal circulation of subtropical moisture that develops over the Southwest during the summer months, typically peaking in July and August before waning during September.

This uptick in moisture combined with orographic lift supports an environment favorable for thunderstorms – often on a daily basis for weeks on end during active monsoon patterns.

The timing, intensity, and regional fluctuations of the monsoon vary from year to year. But in most years, thunderstorm frequency begins to ramp up in Colorado during early July before decreasing around or after Labor Day. 

September is often a great time to summit fourteeners when thunderstorms are less common and before heavy winter snow arrives. However, they still happen on occasion at this time of year, and are more common in the San Juan Range later into the month where monsoon moisture tends to stick around for a bit longer.

Also, in some years, the monsoon onset may be delayed until mid or even late July. When this occurs, you may also have a good window in early July with less frequent thunderstorm activity. But in other years, the monsoon can get going as early as June. 

What Time of Day Should You Hike a 14er to Avoid Lightning?

Thunderstorms are most common during the afternoon hours, but the first storms often develop over the higher peaks by midday. This necessitates a very early start to safely summit and descend a 14er.

The general rule of thumb for fourteeners has always been to plan on summiting in the morning and descending back to treeline by no later than noon to avoid thunderstorms.

This is a good rule of thumb most of the time, but you also want to pay attention to the weather forecast before your hike and cloud/sky conditions during your hike and be ready to adjust your plans. Thunderstorm timing fluctuates day-to-day, and storms sometimes develop before noon or even during the overnight and early morning hours.

Time, Distance, and Complexity of Your Route

It's important to think about your intended route and how quickly you can descend after summiting, or if you have to bail early due to weather.

Peaks involving walk-ups on trails such as Grays Peak and Mt. Elbert involve quicker descents to less vulnerable terrain, compared to more technical peaks such as Longs Peak or Capitol Peak which involve significant time scrambling and route-finding over exposed terrain.

These more technical routes that involve scrambling can take a long period of time to cover a short distance, including on the descent. This should be factored into your planning and decision-making when it comes to avoiding thunderstorms.

More technical fourteeners such as Pyramid Peak often involve slower navigation and are not easy to descend quickly and safely in the event of a thunderstorm. 

Thunderstorm Forecasts and Tracking Tools

When it comes to thunderstorms, it's important to monitor the forecasts before you head out, and to monitor real-time conditions while you're out.

Hourly Lightning and Rain Forecasts

A great place to start is with our 10-day and hourly forecasts, which are available with an All-Access subscription

We have point forecasts available for every Colorado fourteener, and many other non-fourteener peaks as well. In addition, you can use our Forecast Anywhere feature to view forecasts for any location and elevation, including lesser-traveled peaks. 

To view a forecast for a fourteener on the OpenSnow app, tap on the "Search" icon and then enter the name of the peak in the search field. Once the peak pops up under "Search Results", click on it to view the forecast for the summit. 

The hourly lightning forecast graphs show the relative likelihood of lightning for each hour. A small yellow bar indicates there is at least a minor risk of lightning for a given hour, while taller bars and orange and red colors indicate higher lightning chances.

The example below for Wetterhorn Peak indicates a low chance of lightning as early as 10 am with the highest chance of lightning during the 2 pm to 8 pm timeframe. 

Hourly forecasts are available out to 10 days, so you can monitor these forecasts well in advance of your planned hike, and you can also target days with lower lightning chances.

You can also view other hourly forecasts such as temperature, wind, cloud cover, and precipitation. On the precipitation tab, we display forecast 24-hour rainfall for that day under the graph.

This gives a good idea of how much rain could fall with thunderstorms, though keep in mind that rainfall tends to be highly variable by location with thunderstorm setups.

A general rule of thumb is that a forecast of less than 0.10" of rain means that rainfall is likely to be short-lived or light, though a downpour couldn't be ruled out in just the right spot.

A rainfall forecast of more than 0.10" indicates an increased potential for heavy downpours, which is something you also want to avoid in steep/exposed terrain.

On the "Insight" section at the top of the forecast, we also let you know if trails are expected to be wet due to recent rainfall. This is something to consider if you start your hike in the predawn hours, as trail conditions may be muddy and you may get wet if you hike through overgrown brush. 

Forecast Radar

Under Maps, you can also view our Forecast U.S. Radar which is an hourly projection of radar from a high-resolution weather model that goes out to 48 hours from the current time. This forecast radar also updates once every hour for the 1-18 hour forecast and once every 6 hours for the 19-48 hour forecast. 

Forecast Radar is useful to get a general idea of when thunderstorms may develop, the geographic coverage of thunderstorm activity (isolated vs. widespread), and the direction in which thunderstorms are expected to travel.

View → Forecast U.S. Radar

Keep in mind that thunderstorms are dependent on many microscale factors, and have an inherent level of randomness. In other words, the Forecast Radar will never exactly match what happens in reality at a given hour. Therefore, this map should be used to get a general picture of the pattern, but should not be taken literally.

Another trick for determining forecast confidence is to compare Forecast Radar to the hourly forecast for a peak. If the two are relatively aligned, that adds a degree of confidence to the forecast.

But if the two are projecting higher thunderstorm odds at vastly different times, this indicates lower confidence in the forecast and you should factor in an extra margin for error as a result. 

Thunderstorm Tracking on the Mountain

While it's always important to review the weather forecast before you head out, it's equally important to monitor conditions while you're hiking. First-hand visual observations and the use of our app when in cell service (service is often good near or on top of peaks) can go a long way in avoiding thunderstorms.

Keeping a Close Eye on the Sky:

Visually, you will first start to notice small cumulus clouds develop, often by mid-morning once the sun has been out for a little while. These are clues that thunderstorms may develop later in the day, but are not of immediate concern.

Keep an eye out for increasing cloud coverage and towering cumulus clouds that rapidly build high into the atmosphere. When these clouds increase in width/bulk and start to develop dark bases, that is usually a sign of a developing thunderstorm. And in high-moisture environments, these cloud bases may obscure the tops of peaks.

An example of a developing thunderstorm exhibiting vertical growth, dark cloud bases, and becoming thicker/bulkier in width. 

If you see a flat anvil extend outward from the top of a cumulonimbus cloud in a mushroom-like shape, that is a sign that a storm has reached maturity and lightning is possible at any time.

You may not notice this if a storm is developing right on top of you, but it's more obvious if a storm has developed some distance away where you can see the entire structure of the storm more easily.

If you do see a thunderstorm developing in the distance, think about the direction in which thunderstorms are predicted to move that day, and also note any visual signs of whether or not the storm is approaching your location.

Also, if you can see a thunderstorm even at a distance, that usually means that additional thunderstorms could develop in the near future, possibly right overhead. 

This may seem obvious, but if you ever hear thunder or see lightning, that means the storm is close enough to put you in danger – especially if you are on a summit or exposed ridge. If you hear thunder or see lightning, it's time to head down immediately.

Lightning Risk Map

We just added a new tool that is very useful for tracking thunderstorms and thunderstorm risk when you're high up on a mountain (where cell service tends to be better, though this varies by location).

Our Lightning Risk Map shows the real-time lightning risk for the next 60 minutes and recent lightning strikes over the past hour. This is an incredibly useful tool to help you determine if you should turn around due to lightning risk ramping up, and also if there have been any recent strikes nearby.

The lightning risk element of this map uses satellite data to determine the likelihood of new thunderstorm development within the next 60 minutes and can help you make a decision to head down before a thunderstorm arrives or develops over your location.

View → Lightning Risk Map

Current Radar

When you have service, you can also track thunderstorms using our Current Radar Map. This is especially useful for tracking the movement of thunderstorms.

On current radar, yellow-shaded colors usually indicate weak to moderate storms (some lightning and rain possible) and orange to red colors indicate strong storms that may include frequent lightning, heavy rain, and hail. 

View → Current Radar

Note: Big mountains block the radar beam from detecting precipitation close to the mountain tops. During the summer, this usually is a less important issue compared to winter because thunderstorms rise far above the mountain tops and the radar can detect them.

Even so, in some cases, radar signals can still be partially blocked and can underestimate the strength of storms in mountainous terrain (especially in Western Colorado). Therefore, we recommend using both the Current Radar and Lightning Risk Maps to get the best idea of storm behavior.

Putting It All Together

To sum it up, here are the OpenSnow All-Access tools we recommend using to avoid thunderstorms on Colorado 14ers...

And here are the visual cues you should look for in the sky when you're on the mountain...

  • Vertically towering puffy cumulus clouds 

  • Vertically towering clouds that are becoming wide/bulky

  • Dark and ominous-looking cloud bases

  • Flat anvils extending from the top of a cloud in a mushroom shape

  • You can hear thunder or see lightning

Questions? Send an email to [email protected] and we'll respond within 24 hours. You can also visit our Support Center to view frequently asked questions and feature guides.

Alan Smith

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About The Author

Alan Smith

Meteorologist

Alan Smith received a B.S. in Meteorology from Metropolitan State University of Denver and has been working in the private sector since 2013. When he’s not watching the weather from the office, Alan loves to spend time outdoors skiing, hiking, and mountain biking, and of course keeping an eye on the sky for weather changes while recreating.

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