My MH sits out in the Florida sun from September to May every year. But the AC is used almost every day to keep the humidity at bay.
But every spring before I leave. I have to wash the rubber roof, all vent covers, TV & Satellite dishes and Bat Wing to get rid of that green mold that multiplied over the winter.
It even grows on the roof and sides of my fiberglass cargo trailer.
Cover tires,
Window shades, leave roof vents open(Max air cover over vents), exercise generator 2 hours every month, check house batteries water every month.
For the windows you may want to buy from Home Depot those 4' X 8' reflective on one side foam insulation boards about 1" thick. Easy to cut to fit every window and it may help keep some heat out.
I use that on my drivers side windows that face the west all winter.