I see some cars with holes cut in the windshield. I'm guessing it is for the most obvious reason, airflow. Does it make a difference and will it cause a problem in mud, snow, and cold weather? Is it worth doing? I tried doing a search but i couldnt find anything on it.

well i personally wouled do it becuase if your engine is right not to lean not to rich
you should need more cooling, and pluse the body off a truck is like a sheld and with
holls in it that will wecken it.
but i gess its ok puting holls in a road car becuase the boddy is just for looks
and your not doing jump with em so thee body dosent need to sheld anythink

dude agent midget i dont like to flame but learn to spell...but anyway i dont think cutting holes in your windshield will help that much...just cut out the side windows thats what i did on my rusty...it all depends on what ur drivin...

ok thank you very much ill start to listen at school now thanks for the advise

lol.....

depends on wich way the fuel tank is mounted? my mst1 the lid is pointed twoards the front so i HAD to cut a hole in the front. ive seen people cut the grill out and put screen where the hole is to keep debre out but let air in. these 10th scales (most) dont have mud guards so the air gets in there,so there is no real reason to put extras in the windshield...

make sure you put the hole in line with the head...it will optimize cooling.
the way you make the hole will also help keep the body ridged. A round hole or a rectangle that has rounded corners, all cuts in the body should be round with no square corners.

I cut holes in all of my bodies. (all I have is off-road) It helps cool the engine, and allows access to fuel door, so you don't have to take the body off to refuel. As far as protetction for the truck, as long as you don't cut them too big, and try to stay 1/2 inch from any corners, it shouldn't compromise the integrity too much.
If you are running in very cold weather(below freezing), you might want to cover the holes to keep some heat in.
It has been my experience that dirt, mud, snow, and everything else that you drive over/through, WILL get inside the body, and all over your stuff. The best advise is to protect each individual component.
And if you run in the snow, be prepared to do alot of bearing maintenance. Especially if you run on any sanded/salted snow. That stuff will make short work of bearings.
Use a temp gun to monitor temp in cold weather, and if you need to, wrap the cooling head in a sock or foil tape to keep temps over 200 degrees. Be cautious of leaning the engine to get the temps up, as you could fry a piston that way.
Good luck and have fun, and if you crash really bad, take pics