The rule
Roof Maxx says it's applied on a dry day with the temperature above 36°F. The roof needs to be dry and clear of snow and frost. Roof Maxx says the treatment absorbs into the shingles within about 30 minutes.
What that means here
In Champaign-Urbana, spring and fall are the easy seasons. Mild winter days often qualify too. We watch the forecast and schedule around it, and the treatment itself takes 30 minutes to a few hours, so a single good day is enough.
Use the wait well
If it's too cold to treat, it's still a good time for an inspection from the ground or a free inspection on the roof when it's safe. Clear gutters and valleys of leaves before winter so water drains off the roof instead of sitting on it.