Yes... its true, the FirstBike is intended for all seasons, even in the Snow. Get the optional ski kit for those wintery days! Ski kit includes two skis.
Our own son LOVES the ski kit and we find it performs very much like the bike does (not as fast as we expected) especially in slushy snow. The balance is very similar to the run bike and he was able to ride even decent slopes without any troubles at 2.5 years of age!