Minnesota's bitter winter has overstayed its welcome for many, but it has been good for the state's air quality.
The Minnesota Pollution Control Agency has not had to issue any air quality alerts this winter.
Cold fronts clear out fine particles in the atmosphere, said Rick Strassman, who supervises the MPCA's air monitoring unit.
Minnesota has experienced more than its share of these cleansing waves.
"This winter in particular it's been very active with storm fronts and the Polar Vortex bringing in all this cold air. And with that cold air is cleaner air; typically all the Canadian air masses are much cleaner," said Strassman.
Minnesota has had a few more "moderate" air quality days during the first two months of 2014, compared to the same period last year. But Strassman said overall Minnesota's air quality has improved significantly in the past three years, likely due to more active weather patterns.
Once temperatures warm up and more moisture moves into the state, pollution levels could move in to the unhealthy range quickly, if air movement in the atmosphere stalls, he said.