Denver, Colorado – A G4 (Severe) geomagnetic storm, in effect for Jan. 20, is expected to reach Earth as Arctic cold spreads into the Rocky Mountains, prompting increased monitoring of power systems and other critical infrastructure across high-elevation and rural regions.
According to the NOAA Space Weather Prediction Center, a coronal mass ejection, or CME, launched from the Sun late last week is forecast to arrive late Sunday into Monday. Severe geomagnetic storms can interfere with power transmission systems, satellite operations, GPS accuracy, and some radio communications, particularly across regions with long transmission lines and sparse grid redundancy.
The storm watch includes Colorado, Wyoming, Montana, Idaho, Utah, and northern New Mexico, where cold temperatures, mountain terrain, and wide geographic spacing between substations can increase operational challenges. While NOAA officials stress that widespread power outages are not expected, the timing coincides with an Arctic outbreak forecast to bring below-zero temperatures, dangerous wind chills, and heavy demand on heating systems.
For most residents, the solar storm itself will not be noticeable. Experts explain that the concern lies in the overlap of extreme cold and geomagnetic activity, which can reduce the grid’s margin for error when electricity demand is high and equipment is already operating in harsh conditions.
Utilities typically increase system monitoring during geomagnetic storms and cold-weather events, with precautionary actions taken to protect transformers and maintain stable power flow. Residents are encouraged to follow standard cold-weather preparedness guidance, including winter travel readiness, keeping electronic devices charged, and preparing for prolonged cold.
Cell phone service and internet connectivity are expected to remain largely unaffected.
As a secondary effect, auroras may be visible across northern portions of the Rockies, particularly in Montana and Wyoming, if geomagnetic conditions intensify.
Geomagnetic activity could taper into Tuesday, even as cold conditions persist across much of the western interior.
