I longboard commute everyday in NYC. rain or shin. Once you have learned to kick with both legs the skateboard instantly becomes an extremely attractive option. If the wheels are exposed simply cut a rubber maid lid from the appropriate sized container. Flip it over, drill the 4 holed pattern and you are set to ride in rain. Groved wheels will help as well. Simply over does the wheels with T9 lubricant post ride and spin them. it goes without saying that the cheapest bearing should be used in rain and that a dedicated rain board is most helpful. See more soon on my up coming blog and website.
http://www.centralparklongboarder.com