Colorado climate and weather

Lightning from a Colorado thunderstorm
Thunderstorms bring lightning to Colorado's Front Range in July 2011. | Photo by Justin Balog / flickr.com

By Sue Deans

The state’s coffers would be full if a dime were dropped in every time someone said, “If you don’t like the weather in Colorado, just wait five minutes.” Snow, rain, hail, wind – all can develop within a short time and change conditions dramatically, or temperatures can drop from temperate to below freezing in just a matter of hours.

This volatility comes largely from the transitions from high mountains to flat plains, affecting the movement of air through the state and consequently the weather.

Rectangular-shaped Colorado is the eighth-largest of the 50 United States, with an area of 104,247 square miles. Elevations above sea level range from 3,315 feet at its lowest point, the Arkansas River, to 14,440 feet at Mount Elbert. The mean altitude is 6,800 feet, making Colorado the highest state in the union.

A little less than half the state is occupied by the high plains in the east, with the Rocky Mountains passing through the middle of the state from north to south.

Fifty-four of those Rocky peaks are the “Fourteeners,” 14,000 feet or higher. Heading west from the state’s eastern borders with Nebraska and Kansas, the plains slope upward, reaching elevations between 5,000 and 6,000 feet. Denver, the capital, lies at the foot of the mountains at 5,280 feet, a mile high. Thus the nickname “Mile High City.” Several plaques noting the spot that is exactly a mile high have been placed on the western steps of the state Capitol, but occasionally are moved when even more exact measurements are obtained.

While the foothills and mountains range from 7,000 to more than 14,000 feet, the terrain around them includes valleys, high parks, mesas and canyons, creating a multileveled landscape carved out by wind, water and ice. Colorado’s major rivers, the Colorado, Rio Grande, Arkansas and Platte, begin within the state and flow outward. The Continental Divide passes along the Rockies, marking the separation between waters that flow to the Atlantic Ocean and those that flow to the Pacific Ocean.

All these geographic factors result in a climate that is generally cool and pleasant, with more than 300 days of sunshine a year. At any given time, conditions can vary widely from one area of the state to another because of differences in elevation and because of air currents flowing around mountains and valleys.

As the Western Regional Climate Center describes it, “The difference (35 degrees) in annual mean temperature between Pikes Peak and Las Animas, 90 miles apart, is about the same as that between southern Florida and Iceland.” Cubres, a town in Colorado’s southern mountains, gets nearly 300 inches of snow a year, while less than 30 miles away, Manassa in the San Luis Valley receives less than 25 inches. Weather patterns are also affected by the orientation of mountain slopes to prevailing winds and by the effect of topographical features in creating local air movements, the WRCC says.

Because the state lacks large sources of moisture in key areas, lower elevations get little precipitation. The state’s annual precipitation averages 17 inches of moisture per year, but it can range from only 7 inches in the southern San Luis Valley to more than 60 inches in mountain locations.

Snow on Snowmass, Aspen Highlands and Maroon Bells
Aspen Highlands (left) and Maroon Bells can be seen from the top of Aspen's Snowmass ski area. | Photo by Zach Dischner / flickr.com

Winter storms coming from the north tend to be accompanied by frigid arctic air. Those accompanied by strong northerly winds that come into contact with moist air coming up from the south can give birth to blizzards. At times, conditions in one part of the state can be warm and dry while elsewhere snow is falling and winds are howling.

Also prevalent in the winter are the legendary Chinooks, warm and strong westerly winds that can raise temperatures 25 to 35 degrees in a short time. Weathercasters sometimes call these “the warm before the storm,” as they frequently usher in snow. Towns along the foothills, such as Boulder, Golden, Evergreen and Fort Collins, at times experience hurricane-force winds, gusting over 75 mph.

Usually Colorado’s snowiest months are in the spring, March and April, when moist air from the south enters into the state. The monsoon flow common in late summer can bring heavy rains.

On the plains, 70 to 80 percent of the annual precipitation falls during the spring. Thunderstorms are sometimes heavy and sometimes accompanied by hail or occasionally a tornado, often damaging crops, buildings and vehicles. In a dry year, the winds can blow up into dust storms.

Winter temperatures tend to be milder in southern Colorado than elsewhere. The foothills tend to be cooler in the summer and warmer in the winter, and the higher the elevation, the better likelihood of precipitation.

The mountains cause temperatures in the western part of the state to vary widely within short distances. If you’re visiting the mountains, take warmer clothing, even in the summer. In the western half of the state, June is the driest month. On the plains, though, June is one of the wettest.

Almost everywhere, the landscape cools at night. The low humidity makes even hot days feel more pleasant than in humid climes.

Weather to watch out for:

• Tornadoes almost never occur in the mountains or in the western part of the state, but in stormy weather funnel clouds can be spotted over the sparsely populated plains and occasionally one will touch down, threatening property and lives. To stay safe, remember to “get in, get down and cover up,” as the National Weather Service recommends. If you’re driving in open country and see a tornado, drive away from the tornado’s path, time permitting. Do not take shelter beneath a highway overpass. If you’re in a car and there’s no time for action, stay buckled in and crouch down, or leave the vehicle and lie in a ditch or culvert away from the vehicle and protect your head. But remember that the worst place to be is outside in the midst of flying debris.

Colorado columbine
The columbine is Colorado's state flower. | Photo by Jerry W. Lewis / flickr.com

• Mountain thunderstorms can turn into dangerous flash floods, as can spring storms fed by melting snowpack. In the early years of Colorado, before technology was used to forecast weather and manage waterways, dozens of lives were lost in floods in Pueblo, Colorado Springs, Morrison, Denver and other cities. More recently, the July 30, 1976, Big Thompson Flood killed more than 140 people along the Big Thompson River in a narrow canyon between Estes Park and Loveland. Signs throughout the state warn drivers to climb to safety in the event of a flash flood, not to try to drive out of it.

• In dry years, wildfires can cause significant damage, especially if they occur during windy conditions. Visitors should pay strict attention to fire danger warnings and avoid campfires, cigarettes and matches in areas of tinder-dry plains and forests. Firefighters risk their lives routinely to help fight the unpredictable blazes. In a 1994 fire, 14 firefighters were killed on Storm King Mountain near Glenwood Springs when a relatively small blaze changed direction abruptly.

• Officially, a blizzard is defined as large amounts of snowfall or blowing snow, winds of 35 mph or more, and visibility of less than a quarter mile. In those conditions or in any heavy snow event, pay close attention to forecasts and warnings, and avoid traveling if at all possible. Take food, water, warm clothing, a winter survival kit and a GPS/cellphone. If you become stranded, stay with your vehicle. Frequently, officials will close highways if conditions become too dangerous.

• Avalanches can close roads in the high mountains, especially if the snowpack is unstable due to cycles of melting and freezing. Skiers and snowmobilers should be especially watchful.

Ingram Falls near Telluride draws water from high-mountain snow fields. | Photo by Richard Hurd / flickr.com

Water from the skies and the snowmelt is managed carefully, used in the homes of residents on the more heavily populated Front Range and to irrigate crops on the plains. The growing season in northeast Colorado averages 140 days and in the southeast, 160 days. Crops include wheat, corn, alfalfa, sugar beets, potatoes and fruit in the north, and in the south, vegetables, melons, sugar beets and alfalfa. Cattle and sheep are raised at lower and higher altitudes. On the western slope, with a longer growing season of 160 to 190 days, more fertile valleys grow fruit, and a thriving wine industry has evolved in the Grand Junction area.

Of course, tourists take advantage of climatic conditions to ski, raft, hike, climb, camp, fish and hunt. But as the WRCC explains, “The principal attractions of the mountains, however, are sight-seeing and the relief they provide from the high summer temperatures at lower elevations.”

For more information on Colorado’s climate, see:

Western Regional Climate Center
Colorado Climate Center
Rocky Mountain Climate Organization