yesterday I carried my racket bag thru a snow with temp about -3°C...should it effect the material properties of /damage the racket?
Unless your racket is made of water, it shouldn't affect the molecular structure of the racket in any way. If anything is vulnerable to temperature fluctuations, it's probably the string job. You'd be wise to let the racket warm up a bit before playing.
maybe paint works as a shield...but i think it's still not a good idea to expose ur rackets to the extreme temperatures frequently
Maybe it's just being Canadian, but I don't consider -3 degC extreme. If anything, it would be rapid fluctuations in temperature and then stressing the frame that would affect it. But the passive warming of a racket to room temperature over 10 minutes shouldn't be a big stress. On the other hand, maybe you have found the real reason why Canadians are not world badminton contenders!