National Weather Service United States Department of Commerce

Flash Flooding Possible in the Southwest; Very Hot in the South and Northwest

Monsoonal activity will elevate the potential for flash flooding impacts especially in complex terrain, burn scars, and urban areas across much of the Southwest and Intermountain West along with the central and southern Rockies into next week. Very hot conditions cover much of the interior Northwest, south-central, and southeast portions of the CONUS into the weekend. Read More >

Denver's 2019 Climate Year in Review

Denver began 2019 under the influence of weak El Nino conditions which began in the fall of 2018 and persisted through the summer of 2019. This weak El Nino episode gradually transitioned into a ENSO neutral environment (EL Nino - Southern Oscillation) in the summer 2019 and is currently the environment the northern hemisphere finds itself in as we start 2020. In general, El Nino conditions bring wetter than normal conditions to the Front Range and eastern Plains of Colorado, primarily in the spring and winter months. When in La Nina environments, near to below average precipitation is often experienced along the Front Range and high plains region east of the Rockies. ENSO neutral environments, along with the transition into neutral and out of neutral, have also been known to occasionally bring dry and wet seasonal extremes to the Rocky Mountain region.

For the weather parameters of precipitation and temperature, 2019 finished wetter and cooler than average. After 3 years of below average precipitation, Denver wrapped up 2019 with an above average total of 15.51" inches. This is 1.21" above the normal of 14.30 inches (NCEI 1981-2010). The previous year of 2018 ending with a scant 8.53 inches. As for temperatures, 2019 was the first year since 2013 where the year finished below the annual average. The average annual temperature in Denver for 2019 was 49.6°F, which was 0.9°F below the 148 year average of 50.5°F. This is 0.8°F below the current NCEI 1981-2010 average 50.4°F.

Precipitation:

The year of 2019 got off to a wet start as a cold and active weather pattern developed over the mid-latitudes of the western United States. January, February and March all finished with above average precipitation along with a healthy contribution to the second half of the 2018-19 seasonal snowfall totals. After slightly below average precipitation in April, May followed through with the year's highest monthly total of 3.23 inches. Climatologically, May and July are Denver's wettest months of the year, so having May as 2019's monthly winner in the precipitation category is not uncommon. As we transitioned into the warm season months of June and July, precipitation came in near average for both months with totals landing slightly above their respective monthly averages. It wasn't until August when the commonly experienced summer dry spell arrived. This warm and dry period lasted through September and into early October. As a persistent ridge of high pressure held firm over the Great Basin, Desert Southwest and Rockies in late summer 2019, the back half of the North American Monsoon was also brought to a rather quick end over the region. When dry high pressure dominates the months of September and October in Colorado like it did in 2019, spectacular fall-like, calm and mild conditions are nearly always experienced. This all came to an abrupt end in the last week of October when an Arctic airmass brought frigid temperatures and snowfall the Front Range, including Denver. This cold winter storm system brought much needed precipitation and saved the month of October from being the 3rd month in a row with well below average precipitation. Like clockwork, in the last week of November, a cold and very moist winter storm hit the Front Range a few days before Thanksgiving. The moist storm system brought snowfall totals in excess of 2 feet to many locations along the northern Front Range. On a percentage basis, November 2019 came in 115% of average, which it mostly owed to the pre-Thanksgiving storm where nearly an inch of water content was received in the snowfall in Denver. After the two fairly significant winter events of October and November, December came in drier than average as a pattern shift across the northern hemisphere mainly provided persistent dry high pressure over the western United States through the end of the year.
 
                     
                     

 

Temperatures:

Across the high plains east of the Rockies, wet conditions often coincide with below average temperatures. This was certainly the case in the winter and spring months of 2019. Most notable were the months of February, March, May along with October later in the year. Both May and October landed in the "Top 10 Coldest Months" category. As two strong and cold storm systems arrived in May, widespread precipitation and snowfall was brought to the foothills and Front Range, the month came in 7th coldest in Denver's 148 year history with a cool monthly average of 51.6°F. Later in the year, in typical mountain-west fashion, a strong and sharp pattern change brought two Top 10 average monthly temperatures for both September and October on opposite ends of the temperature spectrum. After September's 2nd warmest month in Denver History, and Arctic blast hit the final week of October taking that month to the 4th Coldest in Denver's 148 year history. September ended the month with a warm 69.3°F average with October taking it the opposite extreme ending with a cold 43.7°F average.  

                       

 

Snowfall:

The cold and active start to the 2019 brought mostly evenly spaced storm system to northern Colorado in January and February. Three strong storm systems brought snowfall to Denver in the short month of February alone which allowed the month to experience 135% above average snowfall. With March climatologically known as the snowiest month in the Mile High City, March certainly did not disappoint the snow and winter lovers. The month came in 21% above average, however what was most notable was an extremely strong and historic storm system which brought widespread blizzard conditions to northeastern Colorado. The storm did not bring excessive snowfall to the Front Range, however the winds associated with the deep closed low was one for the record books as persistent 60-80 mph northerly winds hit the eastern side of the Mile High City pounding northern and eastern Colorado with white-out conditions. With two cold and active months of February and March combined with additional snowfall arriving in April in May, the following early snowfall season of 2019-20 followed through with the cold and moist theme. Arctic cold, along with good snowfall, arrived in last week of October. This cold event, paired with the moist and snowy pre-Thanksgiving November storm, brought additional water to the South Platte Drainage Basin. In the final month of 2019, as it was looking like a record or near record lack of  snowfall for December, another late month storm system brought the final snowfall for 2019 as Denver ended the final month with 2.8 inches.

 

                     

 

When 2019 ended, the average annual temperature for Denver finalized at 49.6°F, which is 0.8°F below the NCEI 1981-2010 annual average of 50.4°F. For the full 148 year record, 2019 was 0.9°F below the average of 50.5°F. This tied for 38th coldest in Denver`s 148 Year temperature history along with 1965, 1964, 1962 and 1886. The coldest year in Denver`s weather History was in 1912 with an average annual temperature of 47.6°F. The warmest year was 1934 with an annual average of 54.8°F.

 

                 Denver's 148 year history of Average Annual Temperatures & Precipitation from 1872 through 2019