Our tennis meetup group, "Tennis Portland", has been playing since 2007.
Dues are used to pay real costs: we pay to http://www.meetup.com/about corporation. "Annual membership": you can play for one year from the payment date.
We play all year long and we have never had a need for covered courts but we can book covered tennis courts if a long rainy wet period occurs.
You can see our archive (calendar) of winter meetups: they were fabulous.
You are welcome to come and try us: play with us a couple of times before paying dues.