How much snow does it take to equal an inch of rain?

A sentence in a recent Associated Press story about the lingering drought over much of the United States:

Farmers embrace snowfall as a means of recharging soil moisture in time for each spring’s corn and soybean sowings, with about 20 inches of snow equating to just an inch of actual water.

That number seemed awfully high to me, so I called the National Weather Service office in Wichita and also conducted some research. The answer, predictably, varies from snowstorm to snowstorm and is driven by the air temperature at the time storm moves through.

The ratio in southern Kansas is most commonly about 12 to 1 – or one foot of snow equaling one inch of rain.

Here’s a chart showing the ratios of rain to snow, provided by the weather service: