My Toyota Celica never gets to full running temperature if its below freezing and it takes about 20 minutes of idle to get a little warm air flowing inside. If I drive at highway speed for an hour or so, the water temperature will fall and eventually stop providing anything more than luke warm air, not enough to maintain a reasonable temperature in the cabin.

Would a different ratio of coolant to water help? Maybe I should just block off a large section of the radiator with cardboard on the cold days and make sure not to run the A/C so the coil doesn't get too hot? I normally run 50/50 coolant ratio.

I live in central Texas, it doesn't get cold much, but I'm a south Texas native, 55 degree and I'm putting on layers and have the heater cranked in my car. When it gets to the teens, 20s and 30s I'm absolutely miserable, just looking to avoid as much of the painful cold as possible.
It actually has a fairly new thermostat, replaced it this summer with the option 10 degrees cooler than factory. It's always done this. When its cold, the engine doesn't produce enough heat. Had a friend with a Mitsubishi Eclipse that did the same thing when it was really cold.

It blows luke warm, because the water temperature at the Cyclinder head hovers around 120 degrees.