I was told, or maybe read, when I first considered RV living, that one of the things that can be a constant battle, is HEAT. No problem in the cooler months, but when it's warm outside, its generally HOT inside.
Thankfully most modern RV's have air conditioning units on top to help keep things comfortable inside, but they do take quite a bit of power to run, require 110 power, so if you're not connected to shore power that means running your generator, and can be rather noisy. It's a somewhat soothing white noise hum and whoosh type of sound, but if you want to watch a movie at the same time... well you get the idea.
Some things can help with the heat to reduce how often or how much you need to run those units:
1) Shade - if possible, ask for a space at the rv park or campground that is shaded by trees. This helps a great deal, obviously.
As for your other windows... the same as above holds true. Shading them from the direct sun, especially on the outside before the sun gets IN, will help keep the temp down. You can get fabric covers as mentioned above, but I've also gone to a home supply store such as Home Depot and bought rolled silver bubble insulation, cut it to measure and attached it to the side out to cover the windows with some spring clamps. Its very affordable and does the job well for those really hot periods.
4) Maintain your roof and exterior paint - Remember that your roof gets beat on by the sun all the time. It must be maintained. Keeping it clean, free of dirt, and protected with a UV protectant is a very good idea. The cleaner and better condition it is in, the most it can reflect heat generating sun. Same is true for your RV exterior. If it's clean and has a decent wax on the paint and/or decals, the better it can reflect the heat generating rays.
5) Watch the external temp - when the temp outside drops down below your inside temp, turn off the AC units, open the windows, door and vents and turn on those vent fans. It will push air out the top (heat) and pull in the cooler air from the inside. If your vents don't have those awesome Fantastic Fans, consider getting them! They really help not only with heat but also pulling out moisture from showers, dishes, cooking, etc.
6) As a last heat beating weapon, remember evaporation - Evaporation reduces the temperature of things but 10-20 degrees! If you really have a heat issue, you can consider spraying some water on the grounds around your rv. Spray some on the rv itself. Install a mister to your awning or get a portable standing unit. This can be a great help to enjoying the outside area in high temps too.
Enjoy the sun in your rv! And always remember... sunscreen. :)