The Valley could see a cold end to 2010.
A low pressure system is moving into Arizona, with an increased chance for rain Wednesday and Thursday, according to the National Weather Service.
High temperatures will stay in the low to mid 60s, with nighttime lows in the mid 30s to mid 40s.
Much colder temperatures are expected Friday, 12 to 18 degrees below normal. Lows could be in the high teens to low 30s, with highs in the mid to upper 40s.
Friday morning may produce a freeze warning in the Valley and lower deserts.
The state's higher elevations could see blizzard-like conditions this week, especially in the White Mountains, with 4 to 12 inches of snow.
The storms last week mean Arizona Snowbowl outside Flagstaff opened for skiers. The area saw 19 inches to 27 inches of snow in the seven weeks.
Sunrise Park Resort in the White Mountains also opened for business.