I've had DirecTV for almost 10 years. We lost signal due to weather maybe 2-3 times a year max. I have a portable, standard-definition dish and box that I keep in the RV. It works great and now that I got the hang of it, it only takes a few minutes to set up. I bought the box on eBay for around $40. You still need to pay monthly for having that extra receiver on the account, but you can turn them on and off at will. I turn it off during the "off-season" and back on when I need it. You can do it online or call them.
I haven't researched portable high-def options, but my understanding is that Dish has more flexibility there.