Don t leave home without them. Raingear for the dedicated. Look for breathable fabric and rain pants or tights that cinch snugly to your ankles. Gloves provide padding for your hands on longer rides. Helmets are required by law in many states.
Fenders keep the elements at bay.
Knobbly mountain bike tires can be replaced with a street tire or slicks , as they re called. Tools and tubes. A pump , tools for minor repairs and spare tubes should be on your gear list. Clip-less pedals , and cycling shoes provide a better transfer of power from your legs to the bike. Lights are a must for commuting in the dark as the days get shorter and the summer sun fades away.