Is it legal for police to look in a person vehicle for evidenc through a closed window

Yes. It's a visual search. Window open or closed does not matter. Whatever is in pain sight is fair game.

They can look for anything in plain sight if there's probable cause to do so. For example, if you were driving erratically, suggesting the possibility of being under the influence, they can look for signs of alcohol or other drugs. Again, it can't go beyond anything "in plain view" ; they can't intrusively search your car unless they have a warrant.

In a parked car they may look into any window

In a car they do a traffic stop on, they may look in any window, and even phsycially search the area where the driver is sitting for safety reasons ( any area within reach of the driver)
*** this is in Georgia and TN)

If the car is impounded, while they can't "search" it, they do have to ( or allowed to) do a car inventory of all items in the car to be sure everything is returned to the owner.