I got a (I think) Performance Bike wind/rain shell/vest ... it is a (supposedly) water-proof or water-resistant vest with velcroed-on shawl sleeves. I find it really useful because I can peel off bits of it as I ride, then unzip it, then take it off altogether. (Calm down, ladies.)

Of course, I am not one of these-pro-level riders who can change clothes while riding. I pull over and do what I need to and stuff the sleeved or vest in a bag or pocket.

Armwarmers I guess you can leave bunched around your wrists, for those who are too cool for bike luggage.

As people say ... it's a huge range of temps depending on humidity, altitude, effort, sunshine .... What i do is look for stuff my size on sale (closeout and return) so if I have a little stuff I don;''t use much ti didn't cost much, and the stuff I do use also doesn't cost much. You can by a "water-resistant" "technical" nylon shell with seven little ad brochures attached, explaining another truly magical aspect of the garment (it keeps you warm sub-freezing and cool up to 190 degrees, blocks rain but wicks sweat, sings your favorite songs and is kind to kittens and only costs $200) ... or you can buy cheap windbreaker. Usually all you aren't getting is the name and the hype.

Some of the super-tech stuff is pretty good---but unless you are going on an unsupported tour of Tibet ior something, where every gram is important and your garment turning into a hang glider so you can fly to safety really matters ... for most guys riding through areas where if it gets really bad ... they can pull into a store .... some of the worst rides I have been on ... I have been riding home, so I knew even if I got off and pushed, I was Getting Home ... so ultra-light and super-tech and all that didn't really matter.