@Greg197, the seasonality of travel depends on where your listing is. Some locations are extremely seasonal, and some have very little difference between high and low season.
One good indicator is the vacancy rate and nightly pricing of your local hotels.
If there is a large difference between seasons room rates for your local hotels, you can expect that travel is somewhat seasonal.
@Greg197 As @Matthew285 indicated, seasonality is quite location specific. I am in a resort area driven by seasonal great weather and the various events related to that. If you are in a big city where business people must travel to often, seasonality is less an issue. Demand and value are even more important.
What is your market? What are your seasons? Why do travelers come to your area? Good luck!
@Greg197 I also live in the Cape. I listed two of my houses in August. I got no bookings until December 17, 2018. Both houses booked up thru April 2019 with 8 different families. Did you get any booking from April to December? I have a suspicision that our area has a very low summer rental rate. Have you found this to be the case as well?