Not only do you have to do what is safe for you, you need to be comfortable enough to get a good nights sleep. Sometimes for some people AC is a necessity. Cheapest and easiest way is with a small 110 volt unit powered by the grid. Most fish cleaning stations have a plug in. Most lodges near boat ramps have outside plug ins for charging trolling motor batteries. Many northern states have plug ins for diesel block heaters. Most unproved campgrounds have a plug in for the campground host site that may not be occupied or outlets in a nearby restroom you may be able to use. Many public restrooms are now air conditioned so at least you can cool down if the heat becomes an issue. Ask a front desk person, 24 hour restaurant person or an auto parts store if there is a parking spot close to an outlet you can park in for $20 cash for a few hours to get some sleep. Non mechanical methods just aren’t enough for some people in certain situations.