Heavy wet snow vs light snow: why one 6-inch storm weighs four times another

Why is some snow so much heavier?

Snow is mostly air. How much water is packed in with that air depends on how the flakes formed and what they fell through. The USGS puts the common rule of thumb at 10 inches of snow to 1 inch of water, and notes that it varies a lot: 4 or 5 inches of heavy, wet snow can hold an inch of water, while powdery snow holds roughly half the water of average snow, about 20 inches to the inch.

NWS La Crosse calls 10 to 1 an old rule of thumb that is usually off the mark, and notes that snow near the freezing mark has lower ratios, wind breaks flakes into denser snow, and deep cold usually means fluffier snow. Ratios can change a lot within a single storm, which is one reason snowfall forecasts miss. In a heavy, wet Colorado low in January 2018, NWS Marquette measured an average of just 7 inches of snow per inch of water.

How much does 6 inches of snow weigh on a driveway?

Here is the arithmetic, step by step:

1. Water weighs about 62.4 pounds per cubic foot.
2. An inch of water over one square foot is a twelfth of a cubic foot: 62.4 ÷ 12 = 5.2 pounds.
3. Six inches of snow at 10 to 1 holds 0.6 inch of water: 0.6 × 5.2 = 3.12 pounds per square foot.
4. A 720-square-foot two-car driveway: 3.12 × 720 = 2,246 pounds.

The same math at three ratios:

A shovelful here is an 18-inch blade pushed 12 inches through the full 6 inches: 0.75 cubic feet. Clearing the whole driveway that way takes about 480 loads.

Flip it around and the point gets sharper. The same 0.6 inch of water can arrive as 12 inches of powder or 3 inches of slush, and both weigh about 2,250 pounds on that driveway. A shallow wet snow can be as much work as a deep dry one.

What does wet snow do to the person shoveling?

Wet snow doubles or quadruples every lift, and a driveway is hundreds of lifts. Push it instead of lifting where you can, take smaller loads, and rest often. The American Heart Association says people with heart disease or its risk factors should not shovel at all, and notes that cold air raises blood pressure while the heart works hardest. See is shoveling snow bad for your heart.

What does it do to plows and snowblowers?

Wet snow is slow work for machines too. A blade pushing several times the weight moves slower and needs more passes, the snow sticks and packs instead of rolling off, and the ridge at the end of the driveway turns into a dense wall. Snowblower chutes clog with it. Long, wet storms often need a pass during the storm and another after, followed by treatment for the slushy film the blade leaves behind.

What does it do to roofs, trees and power lines?

Every inch of water adds 5.2 pounds to each square foot of roof, and wet snow piles that up fast. Signs of trouble are in roof snow load warning signs.

Wet snow also sticks. It builds up on branches and wires instead of sifting through, and that is when limbs snap and lines come down. Treat any downed line as live, and see ice storm and power outage safety.

Why does wet snow turn into ice?

Wet snow falls near 32°F, so it packs under tires and feet into a slick layer, and any slush left on the pavement freezes when the temperature drops after the storm. Clearing to the pavement before nightfall prevents most of it; black ice on driveways covers the rest.

Wet snow is also more common near the water. Lake St. Clair tilts storms near the shoreline toward wetter snow, as Macomb County snowfall averages explains. After Thanksgiving 2025, NWS Detroit/Pontiac reported snow that came out much wetter and denser than forecast, with totals dropping off quickly near the lakes: Shelby Township measured 4.4 inches, Eastpointe 3.5 and Grosse Pointe Farms, on the Lake St. Clair shore in Wayne County, 1.4.