Blue skies hover over Denver 300 days each year.
“If you don’t like the weather, wait five minutes.” This Denver saying accurately reflects the unpredictability and broad scope of the Colorado climate. Denver has four distinct seasons and each one varies drastically from the others. The majestic Rocky Mountains to the west cause Chinook winds (dry and warm winds) to heat this arid High Plains city, resulting in generally mild temperatures year-round and 300 days of annual sunshine (more than Miami or San Diego).
Though impossible to predict, the following presents a guideline for the general weather conditions of each season in Denver and in the nearby Rocky Mountains, an important part of the Denver culture and lifestyle.
Denver Summer: June-August
Dry heat characterizes the Denver summer, though temperatures do not usually reach scorching and average in the very comfortable 70s-80s. In 1999-2005, drought was a major problem causing water restrictions and brown vegetation, but the Denver summer is beautiful and great for outdoor activities, especially in the mountains just a short drive away where the temperatures cool and wildflowers bloom. In August, fragrant afternoon thunderstorms are fairly common.
Denver Fall: September-October
Denver fall averages cooler and crisp temperatures, but conditions vary greatly to reflect the fickle transition from summer to winter. Autumn leaves are beautiful throughout Denver and even more so in the mountains, where bright golden aspen groves are a popular destination for tourists and Denverites alike. The first snow usually falls in the city in late September through early October, after which snowstorms become unpredictable in frequency and magnitude and alternate with both warm, sunny days and chilly, breezy ones. Denver ski resorts begin opening in mid- to late October.
Denver Winter: November-February
Snow falls sporadically in Denver throughout winter, though usually melting quickly in the persistent Colorado sun—cold or cloudy spells rarely last more than one or two days. Temperatures are surprisingly mild, averaging just around freezing point. The mountains, however, remain snow-capped throughout winter, and skiing conditions are world-renowned but can be quite cold with icy winds at times.
Denver Spring: March-May
March is the snowiest month in Denver, often with the biggest and most unexpected blizzards, and springtime brings the greatest weather variety. In the mountains, spring skiing is warm and sunny, and Denver resorts stay open at least until mid-April. As the mountain snow begins to melt, runoff brings Denver to life with flourishing green vegetation and bright flowers.
The Best Times to Visit Denver
With four distinct and unique seasons, choosing the best time to visit Denver depends on personal interests. For skiers and other snow enthusiasts, winter and early spring are hard to beat for beauty, sporting conditions and continual sun. Fall is the time to see the golden Rocky Mountain aspen trees and to experience warm to pleasantly cool, but not too cold, weather conditions. Springtime weather is the most capricious, which can make traveling tricky but also displays Denver at its greenest. Summer is really the only time to avoid possible snow, and is also the best time for warm-weather activities such as hiking, biking, horseback riding, fishing, rafting or golfing. Denver hotels accommodate all Denver seasons with a mountain flair.
What to Pack
Whether hiking boots or ski boots, outdoor gear is a must, as the best way to experience Denver and the surrounding area is through spending time outside. Overall, Colorado style is more about functionality than fashion. Sunglasses and sunscreen are absolutely necessary no matter the season—the elevation of the “Mile High City” really does make the sun stronger, and during wintertime this intensity is further magnified through reflection off the snow. Clothing-wise, summers are hot enough for shorts and sleeveless tops whereas winters necessitate bulky jackets, hats and gloves. Fall and spring can be a mixture of the two extremes, and so layers of different weights are the best way to prepare.
Denver International Airport Weather
Unpredictable Denver snowstorms hit Denver from October through April, a potential problem and challenge for the Denver International Airport (DIA). As Denver weather is an implicit part of the location, DIA usually deals with snow fairly efficiently; in 2004, for example, DIA ranked first in major airports for on-time arrivals. There can be problems and delays with particularly massive snowfalls, though this rarely happens more than one or two times a year.
— Denver Weather review by Denver native Courtney Winn