You probably think this is going to be a rant, or at least I'm being facetious. I'm not. I really don't mind heading out when most regular people cower inside. True, the weather over the past three days disrupted plans to get some distance work in. A five hour ride when it is raining, windy as heck and 35F would suck and is probably foolish. So you have to roll with the punches and at least get some intensity in. Shorter, intense, sub-glycogen depleting rides let your body generate more than enough heat to stay warm.
High tech clothing helps too. Pearl Izumi AmFib tights perform marvelously in pouring raing. They are not water proof, but use some of the most hydrophobic material I own. They hold air, not water, so maintain a thermal barrier against the elements. Lobster mitts and a windproof balaclava help out with those extremities. Neoprene booties over plastic baggies can keep the feet dry for hours. I do not ride a fendered bike. I use only a flamingo rear fender to keep the derriere dry.
Rain at or just above freezing is the most challenging weather to train in. Any colder, it turns to snow and that is ok. Any warmer, risk of hypothermia is greatly reduced. So when you go out to drill it for 90 minutes, you really don't notice how misserable it is. Just pray you don't get a flat.
So what is the best part of riding in 35 degree rain going sideways? It is what makes nice weather special. Tucson is looking extra special right now: