Wild September Weather in the West

Labor Day weekend in the northeast United States was absolutely beautiful. Full sun, not too hot, perfect weather for the traditional end-of-summer activities that usually fill that weekend. However, early September has been filled with weather conditions that are anything BUT perfect in other parts of the country. Let’s take a look:

Webcam image from the Continental Divide Webcam, located at Glacier Basin Campground in Rocky Mountain National Park, from September 9, 2020. Courtesy: NPS.

Colorado Snow and Cold

After a day with record heat on Sunday, September 6, Labor Day dawned with Winter Storm Watches in effect across portions of the front range of the Rockies.

An anomalously cold air mass surged southward from Canada. This, in combination with a strong upper-level disturbance and plentiful low-level moisture, resulted in the development of a strong area of low pressure which brought accumulating snow to Colorado. Some areas received upwards of six inches of the white stuff, which melted quickly as temperatures rebounded to near normal conditions by the end of the week. While they don’t happen all the time, such wild temperature swings do happen in Colorado from time to time. The National Weather Service compiled a list of the largest one-, two-, and three-day temperature changes at Denver here.

Extreme Heat in the West

All along the west coast of the United States, record heat has persisted into early September 2020. On many days, high temperatures over 100 degrees were widespread. The National Center for Environmental Information maintains a database of the number of records set across the U.S. at stations with over 30 years of reporting history. Types of records broken include: record high maximum and minimum temperature, record low maximum and minimum temperature, precipitation, snowfall, and snow depth. During the first week in September, over 1000 daily record high maximum temperature records were set, and several all-time high temperature records were broken as well.


As a natural result of sustained high winds and near or above record high temperatures, extreme fire danger and poor air quality have been a major problem across the western United States. The map below shows Red Flag Warnings in magenta, which are indicative of high fire danger, and Air Quality Alerts in gray, across parts of California, Washington, and Oregon.

NWS Warnings and Advisories, 9/9/2020. Magenta indicates ‘Red Flag Warning’, gray indicates ‘Air Quality Alert’.

The National Interagency Fire Center maintains an ongoing list of current wildfires, with statistics on each, here. There is also a daily discussion of fire conditions and other resources as well. The Geocolor satellite image below clearly shows many ongoing wildfires and the widespread smoke.

While natural sources such as lightning are sometimes responsible for these wildfires, often times humans are responsible as well. It is especially important to follow the guidance of authorities when this type of extreme fire danger is present, since a single spark, un-extinguished cigarette, or bad decision can be the cause of a wildfire which can cause property destruction, injury and death.

High Winds in Utah

While much attention was focused east of Utah (in Colorado) and west of Utah (along the west coast), a historic downslope wind event occurred along the Wasatch Mountains on September 8. Easterly winds blowing down the Wasatch Mountains in conjunction with the same storm system that was bringing snow to Colorado brought down numerous trees and caused widespread power outages in the Salt Lake City area. The National Weather Service reported widespread wind gusts in excess of 50 miles per hour. The University of Utah reported a gust of 89 miles per hour, and a sensor on I-89 near Park City recorded a gust of 99 miles per hour.

Wind damage in Salt Lake City, September 8, 2020. Courtesy: Deseret News.

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