Guide

Right outsideWeather

Why snow can fall when it is above freezing

November to April

Snow can reach the ground even when the thermometer by the door reads a few degrees above 32 F. It happens because the flakes form in freezing air higher up, and in dry air each falling flake cools the air around it as it shrinks away.

Why this time of year

Snow season runs from late fall into April, and a snowfall can start while the thermometer still reads a little above freezing if the air is dry enough.

How to notice it

  1. When snow starts falling, check an outdoor thermometer. If it reads a little above 32 F, you are watching snow outlast warm air.
  2. Catch a few flakes on a dark mitten or sleeve and look at their size. Big, soggy clumps mean the air is close to freezing or a bit above, because a thin film of water lets the crystals stick together.
  3. Check the reading again after a while of steady snow. In dry air the falling snow can cool the air, and the temperature may drop toward 32 F.

Try this with kids: Catch a snowflake on your dark mitten, look at it fast, then check the thermometer. Is it warmer than 32? Big wet clump or tiny grain?

Sources

  • nsidc.orgNSIDC: snow can still reach the ground when the ground temperature is above freezing if conditions are right; snow will not form if ground temperature is at least 5 C; large flakes need near-freezing temperatures and light winds.
  • weather.govNWS case study Dec 26 2004: 34 F and 41 F stations reported snow; sublimation in dry air holds air at the wet-bulb temperature, snow reaches ground if wet-bulb is 32 or less; temperature fell 34 to 30 F within about an hour of precipitation.
  • wxguys.ssec.wisc.eduUW-Madison Weather Guys: large flakes are aggregates; crystals slightly above freezing get a thin liquid film that joins them.
  • wpc.ncep.noaa.govNOAA WPC: at very cold temperatures crystals tend to be smaller; fluffiest snow near 15 F.
  • bluehill.orgBlue Hill Observatory: long-term average date of first snowfall November 18 (1886-2012), November 20 (1981-2010).
  • bluehill.orgBlue Hill Observatory April 2018: final measurable snowfall April 6.
  • bluehill.orgBlue Hill Observatory spring 2024: spring snowfall 0.7 inches all in April.

Checked against these sources on October 16, 2026.

In the guide for November, December, January, February, March, April

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