there are many kinds of solar cookers, both homemade and puchased. Most of the ones for sale are on the internet...I have one that I purchased since I am in an rv and don't have that many tools with us. I will give you a few sites to look at...
this next site is my solar oven, but I bought it from another site!
there is plenty of reading on these sites...and many more...just google solar cooking.
I belong to two yahoo groups for solar cookers and I have run into people both on there and here in the forum, and other rvers!
If you have any questions just ask..if the sun is out, you can cook, doesn't matter what the temp is, just your oven will get hotter in the summer when the sun is overhead!