Guide

Right outsideWeather

Why frost lasts longest on the north side

November to March

On a frosty morning in the cold months, frost and snow stay longest on the shaded, north-facing side of roofs, walls, and hills, while surfaces in direct sun clear first. The low winter sun strikes south-facing surfaces more directly, and north sides get little or none of it.

Why this time of year

In the cold months the sun stays low in the southern sky, so shade and the direction a surface faces sort the yard into frosty and clear patches.

How to notice it

  1. On a morning when frost is on the ground, go out early and look at a roof, fence, or wall. Note which side is white and which is already clear.
  2. Check the lawn or ground in the shadow of a house, shed, or tree line. Compare it with open ground in the sun a few steps away.
  3. Come back later in the morning. Notice the white patches shrink back into the shady corners and the north sides of things.
  4. If there is a hill, stone wall, or snow patch nearby, see which face holds frost or snow longer. Expect the north side to hold on.

Try this with kids: Find the last patch of frost or snow in the yard. Which way does it face, and what is blocking the sun from it?

Word to know: “Aspect” means the compass direction a slope or surface faces.

Safety

  • Shaded north-side steps, walkways, and driveways can stay icy after sunny spots have cleared, so walk slowly.

Sources

  • ucanr.eduUC Marin Master Gardeners: north-facing direction receives least sun, 'frost may linger here in winter'; cold air pools behind north-facing structures.
  • wpcdn.web.wsu.eduWSU Extension: 'In the northern hemisphere, south-facing aspects are exposed to more direct sunlight than opposite slopes'; applies to small slopes in a yard.
  • explorenaturalcommunities.orgNatureServe and NPS National Capital Region: the sun strikes south-facing slopes more directly; 'Snow melts away faster on south-facing slopes than on north-facing ones.'
  • eoas.ubc.caUBC atmospheric science: low winter sun in the southern sky; 'Insolation strikes the south-facing slope at a more direct angle.'
  • northernwoodlands.orgNorthern Woodlands (New England): north-facing slopes still hold snow when south-facing slopes have lost it.
  • kshb.comKSHB local TV (secondary, safety note only): in winter the north side of buildings sees no direct sun.

Checked against these sources on October 2, 2026.

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

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