Catalyst system

[bigrick7]

Today my check engine light came on . I have a 2001 camry 4 cyl engine auto tranny. I run the code reader and i get code
P0420. code P0420 means Catalyst system Efficiency below Threshold (bank 1). what exactly does this means. also i live in the noetheast we just got hit with heavy snow. could all the slush being kick up into the car cause this problem? thank you for any help.

[jsinton]

It's really cold, you could of gotten snow up in there or something. See if it happens again.