I've lived and cycled in rain in the Pacific NW all my life; I have some advice.

First, 30 and 45 degrees are very different temperatures. My rule of thumb is that when rain is added to a temperature, I dress for 10 degrees lower. So if it's 45 and raining, I'll dress as if it were 35 and add a rain jacket.

Generally, you will get wet. No avoiding that. The question to ask is how to stay warm while wet. From my experience, if you can keep your core warm, your extremities will be okay (maybe not super comfortable, but okay). I favor wool, though some synthetics are nice as well. Stay the heck away from anything cotton. You should have zero cotton on your body if you are riding in the wet.

Wool base layers and wool long and short sleeve jersey's are great (synthetics work okay as well, as long as they are lined and insulated - lycra jerseys do absolutely nothing except add non-sagging pockets under your insulation). Just layer them up as needed under your rain jacket. A good cycling specific rain jacket is a must for cooler temperatures. Showers Pass makes the best rain jackets (used to be Burley before they were spun off and renamed Showers Pass). DeFeet has some good wool stuff for your extremities and baselayers, and Oregon Cyclewear has excellent wool jerseys. I wear sock-type booties over my shoes and wool socks. They don't keep water out, but they trap warmth and act as a wind block. Again, your toes will be fine if your core is warm. For hands, I wear wool gloves most of the time. In lower temperatures or when it's windy, I'll wear wind breaking gloves over a glove liner. Everything's going to get wet, the trick is managing warmth, not dryness. I've tried waterproof gloves; my hands just got soaked with sweat.

For legs, I have insulative tights. It gets wet, but it's manageable, as long as your core is warm. If it's relatively warm, you can get away with insulated leg warmers. You can also layer this stuff up. I've gone out with wool knee warmers under tights before; the combo was pretty sweet. I've used various brands... as long as it covers your legs and has some insulation, I've never had a problem keeping my legs warm under any condition.

For in-between temperatures (too warm for long sleeve jersey, too cold for short sleeve jersey plus long sleeve baselayer), wool arm warmers are pretty nice. In fall/winter I tend to wear these over a long sleeve baselayer with or without a rainjacket.

An insulated skull cap that goes over your ears which you can wear under your helmet works to keep your head and ears warm. I've also gone out with just a regular, thin, wool stocking cap under my helmet. It was a tight fit, but it kept me pretty warm. Adding a thin layer of petroleum jelly to your cheeks and nose when it's raining and in the 30s works to keep your face warm.

Dress in layers and learn to ride over-cold and over-hot. In other words, learn to ride when it's uncomfortable. Sometimes you simply miss, but you learn from experience.

Coldest I've ever been was a race in the Willamette Valley near Eugene. It was low-40s-upper-30s and raining hard the entire 40 mile race and all I had was a short sleeve lycra jersey, arm warmers, and really thin knee warmers. No insulated leg warmers, jacket, shoe covers etc. Pretty much what you see in my profile pic. I think I had short finger lycra gloves for my hands. Before the final climb (race ended on a 2 or 3 mile hill climb) warmed me up a bit, there were points when I couldn't feel anything below my elbows and I was looking over at my hand to guide my finger to shift gears. After the race, we had to ride back down the hill and two of my teammates bummed a ride from a random passerby with a pickup truck because they were shaking so hard they couldn't hold their bikes straight.

EDIT: one thing I just thought of... there is a difference between insulation and wind/rain blocking. You definitely need insulation. You don't necessarily need wind or rain blocking outer layers. A raincoat over a lycra jersey will have you both wet (from sweat) and freezing, even in 45 degree rain. A good wool jersey with insulative under-layers will work just fine even without a raincoat into the lower 40s. This goes for hands and feet too. A pure wind/rain blocking glove is useless unless you have insulation under it in the form of a glove liner. A wind/rain blocking shoe cover is not terribly good unless you have either thick socks over your feet (problem here is you need bigger shoes to fit these socks), or socks which go over your shoe (my preferred solution - DeFeet has these also).