What Is Heavy Snow? Here's How Many Inches Can Fall In An Hour During Major Winter Storms

Major winter storms and lake-effect snow often pack heavy snowfall rates that lead to hefty storm totals, but have you ever wondered how many inches can fall in an hour?

S​nowfall rates of an inch or two per hour are generally considered heavy. That type of snowfall rate typically lowers visibility to a quarter-mile or less, or similar to what you see in the photo below. Travel conditions can deteriorate rapidly in those conditions whether the heavy snow rates produce significant accumulations or not.

But that's just the lower end of the threshold for what qualifies as heavy snow. Next, we examine some more extreme examples, including the U.S. record.

Recent winter storms have produced up to a half-foot in an hour. Let's start with some examples of hefty snowfall rates not associated with lake-effect.

• A major winter storm in mid-December 2020 produced s​nowfall rates of 4 to 6 inches per hour in south-central New York near Binghamton. That resulted in totals near 3 feet in about 12 hours, the National Weather Service said. You can see those heavier snow rates in yellow on the radar image below compared to lower rates in lighter greens.
• I​n March 2017, a winter storm near Burlington, Vermont, produced 5 inches in an hour and 8 inches over the course of two hours.
• A​ location in central Connecticut saw 6 inches in an hour during an early February 2013 winter storm.
• I​n Alaska, a snowfall rate of 10 inches in an hour was tallied at Thompson Pass in early December 2017. The total over 90 minutes was 15 inches, with a 12-hour amount hitting 40 inches.

Amid a winter storm's much larger area of snowfall, the most intense rates are often found in smaller bands and are sometimes accompanied by lightning. These bands may only be 5 to 10 miles wide, and if they persist in one area for multiple hours, totals can be much higher than surrounding areas.

T​he U.S. record is 12 inches in a single hour. That happened in a lake-effect snow band east of Lake Ontario in Copenhagen, New York, on Dec. 2, 1966, according to a list of record snowfall rates compiled by weather historian Christopher Burt in his book "Extreme Weather."

In potent setups, l​ake-effect snow more commonly produces snowfall rates of 2 to 4 inches per hour, and sometimes higher. For example, an early December 2024 lake-effect snow event produced 12 inches in two hours to the east of Lake Erie near Eden, New York.

Lake Ontario is especially notorious for producing intense snowfall rates. That's where all of Burt's various snowfall rate records on the list below are located, except the top spot for 24 hours.

Chris Dolce has been a senior meteorologist with weather.com for over 10 years after beginning his career with The Weather Channel in the early 2000s.