Thousands of people are being asked to evacuate immediately as winds fuel fast-spreading wildfires in Boulder County, Colorado.

       Several small grass fires, sparked by downed power lines amid gusty winds in central Colorado, according to the Boulder County sheriff, have grown into raging blazes Thursday afternoon.

       Louisville, Colorado, with a population of about 20,000, is being asked to evacuate, according to the Boulder Office of Emergency Management. The entire city of Superior, Colorado, with a population of about 13,000 people, is also being asked to evacuate.

       The National Weather Service of Denver/Boulder described the situation in Louisville as life-threatening in an alert on Twitter Thursday afternoon, while urging people to leave immediately.

       Centura Health's Avista Adventist Hospital in Louisville started evacuating its patients, starting with its most critical, a Centura Health spokesperson told ABC News Thursday afternoon.

       Six patients were taken to UCHealth Broomfield, which serves the Boulder area, due to injuries from the fires, a hospital spokesperson confirmed to ABC News.

       David Zelio/AP

       Smoke from a wildfire rises in the background, Thursday, Dec. 30, 2021, in Superior, Colo. All 13,000 residents of the northern Colorado town were ordered to evacuate Thursday because of a wildfire driven by strong winds.

       Eric English/KMGH

       Strong winds are fueling wildfires in Boulder County, Colo., on Thursday, Dec. 30, 2021. Thousands are being forced to evacuate.

       Colorado fire officials told ABC News that the high winds are making it difficult to get aerial resources into the area to fight the fires.

       Wind gusts topping 100 mph were reported in northern Jefferson County earlier Thursday, while parts of Boulder County saw gusts over 80 mph. The city of Boulder also reported wind gusts over 70 mph Thursday afternoon.

       The Boulder area is currently suffering from extreme drought, according to the National Oceanic and Atmospheric Administration and the Department of Agriculture.

       Eric English/KMGH

       A wildfire spreads through Boulder, Colorado, Dec. 30, 2021.

       Colorado Gov. Jared Polis has declared a state of emergency due to the fires in Boulder County, his office said.

       "Prayers for thousands of families evacuating from the fires in Superior and Boulder County," Polis tweeted. "Fast winds are spreading flames quickly and all aircraft are grounded."

       ABC News' Jeff Cook, Dan Manzo, Jenna Harrison and Dan Peck contributed to this report.