I wear these, http://www.sportsmansguide.com/net/cb/cb.aspx?a=366826 pretty good into the 30s, a pair of chaps over that if it's a long ride or getting colder. The Diamond Gussett riding jeans are on my wish list since they'll custom fit the waist...
A positive attitude may not solve all your problems, but it will annoy enough people to make it worth the effort. Herm Albright (1876 - 1944)