IME long term storage outdoors under a cover is actually worse than just parking it outside. They tend to trap in humidity/moisture and are very inviting to pests. Yes they stop water from directly hitting the top of the car in a rainstorm, but then the water flows under the car and will evaporate upwards under the cover and have no place to go, leaving the car damp and musty all the time.
Sure the car will get covered by pollen and get hot in the sun without a cover, but some semi-regular cleaning and even something as simple as window shades or a piece of cardboard over the dash can make a big difference. If you can't park it indoors maybe you could construct a carport or use one of those temporary "tarp garages" (not sure what they're technically called). The only real drawback of using those is that they can collapse under the weight of a heavy snowstorm, which I really really doubt would be a big problem in Houston.
Hah, the only car in my driveway I have under a cover isn't there to protect it from the elements, it is to protect my neighbors from having to look at my smashed up parts car.