White Christmas Calculator — Snow Probability
Enter your location's historical White Christmas probability (the share of years with at least 1 inch of snow on the ground on 25 December) and a time horizon to see how many snowy holidays to expect, the chance of at least one, and the chance of none at all.
%
Probability that Christmas Day has ≥ 1 inch of snow cover at your location
- 1
Annual probability (decimal)
30 ÷ 100 = 0.3 - 2
P(no white Christmas in n years)
(1 − 0.3)¹⁰ = 0.0282n = 10 — each year is an independent Bernoulli trial. - 3
P(at least one white Christmas)
1 − 0.0282 = 97.2
How does this calculator work?
Enter your city's historical White Christmas probability (% of years with ≥ 1 inch snow on 25 December) and a number of years. The calculator applies binomial probability to show: expected count of snowy Christmases, chance of at least one, chance of none, and chance of a perfect streak — using P(at least one) = 1 − (1 − p)ⁿ and Expected = n × p.
Formula
How this is calculated
A White Christmas is traditionally defined as at least 1 inch (2.5 cm) of snow cover on the ground on 25 December. National weather services publish historical probabilities for major cities — for example, roughly 10–15 % in London, 20–25 % in New York City, 50 % in Chicago, and above 90 % in Calgary or Fairbanks. Enter your city's figure (or look it up in your country's climate normals database) as the single-year probability p.
The calculator treats each Christmas as an independent Bernoulli trial with success probability p. Under this model, the chance of getting zero white Christmases in n years is (1 − p)ⁿ, so the chance of at least one is 1 − (1 − p)ⁿ. The expected count in n years is n × p, and the probability that every Christmas in the period is snowy is pⁿ.
These calculations assume year-to-year statistical independence, which is a reasonable approximation over many years but ignores short-term autocorrelation in winter weather. Climate change is also gradually shifting historical baselines in many regions, so treat the historical figure as an editable estimate that you update as better data become available.
Frequently asked questions
National weather services publish historical climate normals. NOAA maintains historical snow records for US cities; Environment and Climate Change Canada publishes snow-on-ground frequencies; the UK Met Office has similar data. Search for "[city name] historical snowfall December 25 climate normal".
It uses pⁿ — the chance of n independent events all occurring. Even with a 50 % annual chance, the probability of 10 consecutive white Christmases is only 0.5¹⁰ ≈ 0.1 %. Requiring a long streak of any event makes the probability decrease exponentially.
No. It is a probability model, not a weather forecast. You supply the historical base rate from climate records and the tool applies binomial mathematics. For actual day-specific snow forecasts, check your national weather service closer to 25 December.
Also known as
TG we-Calculate Editorial Team. (2026). White Christmas Calculator — Snow Probability [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/white-christmas-calculator
TG we-Calculate Editorial Team. "White Christmas Calculator — Snow Probability." TG we-Calculate. 2026. https://we-calculate.com/calculator/white-christmas-calculator.
TG we-Calculate Editorial Team, "White Christmas Calculator — Snow Probability," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/white-christmas-calculator
@misc{wecalculate_white_christmas_calculator, title = {White Christmas Calculator — Snow Probability}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/white-christmas-calculator}}, year = {2026}, note = {TG we-Calculate} }
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