I try to not let the weather dictate when I ride my bike. When the temperature drops or it starts raining I just make adjustments to my clothing and go out for a ride anyway. One item you really need to own for inclement weather riding is a good helmet cover, and my favorite one is the Louis Garneau Bicycle Helmet Cover (H-Cover).
The Louis Garneau Bicycle Helmet Cover is made of a very breathable Stopzone fabric and it does a fantastic job of blocking both wind and rain. This cover stretches to fit all the helmets I own (Bell, Trek, Louis Garneau and a Giro). You might have tried other helmet covers before, but most of the covers on the market that I’ve tried don’t fit my helmet very well. Last year I bought an illumiNITE Helmet Cover and the best I can tell it was patterned after my grandmother’s shower cap—I don’t know who designed it, but they apparently had never seen a bicycle helmet before.
The Louis Garneau Bicycle Helmet Cover is available in two colors: Black or Bright Yellow (Hi-Vis Yellow). Both colors of this helmet have reflective piping to help motorists see you in low-light situations. I wear the bright yellow cover when I am riding on the road because it is hard for drivers to miss. When I am riding on muddy off-road trails I wear the black helmet cover because it will still look good after I wipe the mud off.
With a good balaclava (like the Seirus Combo Clava) and the Louis Garneau helmet cover I have no trouble keeping my head warm in temperatures down to around 20 degrees. When the temperature drops to below 20 degrees I switch over to a skiing helmet (I prefer the Smith Optics Variant Brim Snow Helmet).
The Louis Garneau Bicycle Helmet Cover is available in two sizes: Small/Medium and Medium/Large. This helmet cover retails for around $20 and I have yet to find a better helmet cover on the market.