White Christmas Calculator
Estimate white Christmas probability from average December temperature and historical snow days.
What Is a White Christmas?
A white Christmas traditionally means measurable snow on the ground on December 25. Probability depends on how cold December tends to be and how often snow falls that month.
Simple Probability Model
$$P = \max\left(0,\ \min\left(100,\ (32 - T) \times 3 + D \times 5\right)\right)$$\(T\) is average December temperature in °F and \(D\) is average snow days in December. Colder temperatures and more snow days raise the estimate.
How to Use the Inputs
Use local climate normals if you have them. For example, a city averaging 25 °F in December with three snow days scores \((32-25)\times3 + 3\times5 = 36\%\).
Related tools: Days Until Christmas and Rain to Snow Calculator.
Frequently Asked Questions
Is this a weather forecast?
No. It is a simplified historical-style estimate, not a day-of forecast for Christmas Day.
Why use 32 °F?
32 °F is the freezing point of water. Below freezing, snow is more likely to accumulate and persist.
Can probability exceed 100%?
The formula is capped at 100% so results stay on a simple percentage scale.
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