I would begin advertising in December (could be an outrageous ad, too) and educate your customers about the season and preparing in advance to minimize lead time.

Keep up the campaign in February, or monthly.

Have an offer if they preorder before the spring thaw at a 10% discount, or some other incentive that gets them lined up sooner.

I did an ad campaign for a Florida realtor who specializes in selling to people in the NE states. The front of their marketing materials has a Florida beach on the right, and a guy with his snowblower in a blizzard on the left. The pitch is "How do you get from here to there?" He sends postcards in July and they are fairly persuasive for the fence straddlers who are not yet convinced to make the move.

Preselling is the key in both situations. Good luck.