So people in mountain areas might carry a shovel and blankets in their vehicle in winter too? Do people usually remove them in summer, or just keep them there all year? Would LE find it suspicious to find a blanket and shovel in someone's vehicle in summer, if that place had snowy winters, do you think?
Well, it depends on the person. Everyone has different habits. It's probably affected in part by how much space they have in their vehicle and how they usually use their vehicle.
I know that the winter survival stuff lives in our van year round unless we clear everything out of the back, including the seats, in order to haul something. I've never really checked other people's vehicles but I find it hard to believe that my husband and I are the only lazy people around!
I think car blankets are fairly common and not only for winter use. There are those of us who live with the human equivalent of polar bears and even in the middle of summer, a car blanket for me keeps Mr Grainne happy. Of course, there are fancy-schmancy vehicles that have more individual climate control zones but we don't own one.
So I think LE searching a vehicle in any place that has cold or snowy winter weather would not be surprised to find blankets and a shovel, even in the summer. Unless there was something really unusual about the items, it would probably just be chalked up to lazy drivers.
If someone lived in mountains that get snow, I'd expect to find a set of chains in their trunk but maybe not year round. Chains are bulky and have no other use than to put on the tires when they are required (and travelling with chains is no joy because they generally restrict your speed to about 30 mph or 50 kph). Then again, if it is a vehicle with a large cargo capacity, inertia may easily take over in the matter of chains, too.
Shovels used for snow shovelling are not usually very good for digging in the ground but that's just my midwestern knowledge. What the ground is like to dig in desert areas, I have absolutely no idea. I suppose if it were sandy, a snow shovel could be used but the deserts I've seen seemed pretty hard packed.
Oh! I just remembered! For many years, I had a nifty little folding spade that a friend gave me that was a souvenir from the Soviet Army (we're not going to ask how he procured the item). It was quite well designed which seemed odd considering the general reputation of Soviet design. It was just the right size to dig out two tyre wide trenches. My brother borrowed it back in the early 90s and he has never returned it but he needn't think I have forgotten. I shall have to add a postscript to his Christmas card!
Anyway, those little folding spades are now fairly commonly available and they would work to dig in any ground that you didn't need to use a pickaxe on.