The regular temperature was just 0 in Denver at dawn on Wednesday but it felt more like 19 below.
The heaviest snow is expected in the northern and central mountains early Monday afternoon, according to the National Weather Service.
The September hailstorm was the eighth-most-expensive ever in Colorado.
The National Weather Service says the Denver International Airport recorded a trace of snow overnight, while Boulder saw a tenth of an inch.
Lows could hit 35 in metro Denver as rain will mix with and then change to snow overnight.
A photo of an enormous cloud in Colorado reaps Slovenian meteorologist top honor in National Geographic photo contest.