Originally Posted by PaulRivers

Eh, it varies from person to person. If you have the right gear, you can ride in the rain at 40 degrees, be completely comfortable, and show up dry to your destination. If you don't have the right gear 70 degrees is more pleasant, but you're going to get wet because any rain gear you'd wear will make you so hot you'll sweat and sweat and end up soaked from your own sweat.