The days are getting longer and summer is approaching, but it still gets dark sometimes! Are you being blinded by the lights of the vehicle behind you or are you using your night position? A lot of cars have an automatic rear-view mirror dimming feature, but if yours is a simple car then it may not. Almost all cars should have a tab on the bottom of the rear-view mirror to flip to the night position. You will still be able to see the same stuff, but you won’t be as blind.

This is especially helpful if there’s a larger vehicle behind you or one with very bright lights, but it may be good whenever you want to focus on any dark environment ahead of you. nightMirror

Reference:

DriveSmartBC: Driving at Night in the Rain