The USA
Best time to ski in the USA: natural snow month by month
When natural snow has been most reliable at the 7 resorts Cirque models in the USA, month by month, from eleven winters of weather data.
Every resort Cirque models here
Each cell is one month: the share of days with 30 cm or more of modelled natural snow at mid-mountain over the last 11 winters, from brown (often thin) to deep blue (snow-sure). Blank means almost none.
The short answer
The surest time for natural snow in the USA has been January to April. In those months most of the 7 resorts Cirque models here were snow-sure in at least 9 of the last 11 winters, meaning mid-mountain had 30 cm or more of modelled natural snow on at least 90% of days.
Month by month
November: none snow-sure in any winter. Most natural snow at Big Sky (24% of days), Jackson Hole (23% of days), Mammoth Mountain (10% of days).
December: 0 of 7 snow-sure. Surest: Jackson Hole (7 of 11), Big Sky (6 of 11) and Vail (4 of 11).
January: 5 of 7 snow-sure. Surest: Jackson Hole (11 of 11), Vail (11 of 11) and Big Sky (10 of 11).
February: 7 of 7 snow-sure. Surest: Jackson Hole (11 of 11), Alta (11 of 11) and Vail (11 of 11).
March: 7 of 7 snow-sure. Surest: Jackson Hole (11 of 11), Alta (11 of 11) and Vail (11 of 11).
April: 6 of 7 snow-sure. Surest: Jackson Hole (11 of 11), Alta (11 of 11) and Vail (11 of 11).
May: 1 of 7 snow-sure. Surest: Big Sky (10 of 11), Mammoth Mountain (8 of 11) and Jackson Hole (7 of 11).
June: 0 of 7 snow-sure. Surest: Mammoth Mountain (2 of 11), Big Sky (0 of 11) and Jackson Hole (0 of 11).
Resort by resort
Alta, USA, 2,600–3,216 m: snow-sure January to April.
Aspen Snowmass, USA, 2,473–3,813 m: snow-sure January to April.
Big Sky, USA, 2,072–3,403 m: snow-sure January to May.
Jackson Hole, USA, 1,924–3,185 m: snow-sure January to April.
Mammoth Mountain, USA, 2,424–3,369 m: snow-sure February to April.
Stowe, USA, 390–1,339 m: snow-sure February to March.
Vail, USA, 2,475–3,527 m: snow-sure January to April.
Questions
When is the best time to ski in the USA?
For natural snow, January to April. That is when the most resorts Cirque models in the USA have been snow-sure over the last 11 winters.
When does natural snow become reliable in the USA?
The first month in which any resort Cirque models here was snow-sure in at least 9 of 11 winters is January. Resorts open on their own dates and many use snowmaking earlier.
Which resort in the USA has the most reliable snow?
Of those Cirque models, Big Sky: mid-mountain was snow-sure in 5 months of the year.
Does this include snowmaking?
No. These are modelled natural snow figures only, from ERA5 weather. Groomed pistes with snowmaking often ski better than this.