I bought a load of chinese granite "Bianco Cordo" about 1 cm thick 30 cm x 60 cm.

It's polished white/grey granite. They are placed outside where rain, frost and
temperature ranges from -20 (january) to +30 (right now). After having set some
plates I noted the granite plane color change slightly. It was probably mortar
moisture seeping from below. The polished top did to get any moist. Next day the
discoloration has disappeared. It probably just evaporated since its +30
centigrade now.

Will there be problems in winter? Will the granite crack from frost changes? I
thought granite behaves well in winter.