You mentioned temporary, but also mentioned cutting a hole in the roof to vent it, which sounds more permanent.
I looked into how to keep my vehicle cool with my dog and ended up with a small window AC in the right rear side window and small Honda Gen in a rear cargo box. Ive been using it for about 4 summers and am very satisfied with its performance. No permanent changes to the vehicle, but its secure and takes up effectively zero room inside. I set it at 61 or 62 degrees, whatever its lowest setting is and the dog stays quite happy, everything in the vehicle feels cold when I get back in.
I painted the outside part of the AC to match the vehicle color, I get a little less pointing and picture taking, but I really dont care much, as it works rather well and I can take my dog shopping or whatever around town and on the road I dont have to worry to go in and eat, use the facilities, shop, whatever. On Eco mode the gen uses about a gallon of fuel in 6 hrs to run the gen. Its also pretty handy to have power if I want to use power tools for projects. This is one of the best modifications to my vehicle Ive ever made.
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