Here, we actually have to keep several blankets and a sunshield in the vehicle from early spring onwards. They live in the vehicle permanently but get most use in the summer months. The first blanket is for the steering wheel and dash board, the second is for the drivers seat and the third for the passenger seat. All car windows in Australia are UV protected, but they also usually end up with see through cloth shields on them as well. Rear doors often get left on with drivers driving around with them in situ. Almost everyone uses the very effective reflective sun shields on the windscreen. Interval mirror and both visors hold them in place when the suckers give up the ghost.
Curiously sunroofs are not called sunroofs and are always closed with the liner pulled closed as well. They are called moonroofs for obvious reasons. I think we've only used either one once and that was to stick some wood through! We bought straps for the roof rack very quickly!
In our main vehicle the seats are 'leather' because we have heated seats (for my back). It's lethal for 9 months of the year.