Not a warm heat

I have a 2000 T/A WS6 when I turn on my heater I am not getting a very warm heat. If it is very cold outside below 35 deg. the engine temp guage only goes up to around 150 deg. During the summer the normal operating temp is around -+205 deg. I have looked at the system and it seems to be fine I have no trouble with my air conditioning that works fine. Any ideas on what it could be or does anyone else experience this? I sit in my girls Saturn and turn on the heat and it just about burns the hair off my legs.

Thermostat