Ice dam risk in Grain Valley, MO

How often ice dams form in Grain Valley

5.2 dam days a winter

Moderate risk. On an ordinary house in Grain Valley, conditions for an ice dam come on about 5.2 days in a normal winter, mostly in January and December.

Grain Valley averages 13 inches of snow a year and about 20 days with snow on the ground. Most of it comes and goes within a few days. The conditions that make a dam need all three at once: snow, cold at the eave and heat above it.

What your attic does to that number in Grain Valley

Attic	Dam days	Risk
Air-sealed and well insulated	3.2	Low
Typical, some insulation, not air-sealed	5.2	Moderate
Older or poorly insulated, warm attic	7.6	Moderate

The attic matters less in Grain Valley than in colder towns: there are only 2.0 days a winter between a typical attic and a sealed one.

What to do about ice dams in Grain Valley

Check the gutters before the first snow and clear them, so meltwater has somewhere to go. If you see icicles thicker than a finger along the eave after a storm, that is the early sign to look at the attic.

Snowy places are not always the worst: why snowfall misleads.

Grain Valley winter, month by month

Month	Snow (in)	Days on ground	Dam days
January	3.6	7.6	2.4
February	2.6	4.0	1.0
March	1.7	2.0	0.3
April	0.2	0.2	0.0
October	0.4	0.2	0.0
November	1.2	0.8	0.1
December	3.5	5.2	1.4

Grain Valley next to nearby towns

Grain Valley ranks 12 of 80 Missouri cities here for ice-dam days, behind Maryville at 9.3 days.

Blue Springs, MO 3 mi, 5.2 days
Independence, MO 9 mi, 5.2 days
Lee's Summit, MO 11 mi, 5.2 days
Raytown, MO 13 mi, 5.2 days
Grandview, MO 19 mi, 4.6 days

Where these numbers come from

NOAA 1991–2020 climate normals from Independence, 9.7 miles from Grain Valley. A dam day is a day with snow on the roof and freezing at the eave while heat or sun melts the snow above it. This describes a normal winter, not this one.