How many challenges will there be in a given winter?

From December 1 to March 31, there may be up to 30 challenges. They’ll take place mornings from 6 a.m. to 10 a.m. or evenings from 5 p.m. to 9 p.m. on especially cold days. On a given day, there may be:

• no challenge
• only one challenge in the morning
• only one challenge in the evening
• two challenges: one in the morning and another in the evening