The List season runs April thru October. The "reason for the season" is the climate difference accross the country. Folks in Florida could have quite an advantage over those in Minnesota. Frankly, the wind in Florida mitigates any conceivable advantage there but that's another story....

From the rules:

The List is contested on a yearly basis within a specific time frame, called The List season. The List season is April 1 through October 31. If April 1 is Sunday, March 31 will be included. If October 31 is Saturday, November 1 will be included. Competitors are awarded List Points every time they compete at a sanctioned match within The List season.