Cold Weather Coolant Temp Gauge
 

I started noticing this late last winter (I don't live in an area that gets extreme cold) where on a cold morning, say below 30 degrees, the coolant temp gauge would take a very long time to raise off the bottom and get to where it usually is, which is near the halfway mark. when I say a long time, I mean drive 10-15 miles on the highway at 60mph. The colder it got, the worse it was. But I always got heat from the heater, although maybe not quite as burning hot. I accept the fact that its going to take a few minutes in order to begin putting out hot air...the air gets warm....but when the gauge needle is at its usual halfway mark the heat can be truly hot where I have to back it off.

Now, of course, I never have this problem in the summer. Problem is, my warranty has about 6 weeks left. Can this type of issue be tested/checked accurately if its not 30 degrees ambient temp? I'm thinking maybe engine thermostat, but if that was stuck would I still get hot air if the hot coolant isn't getting to the heater core? Any other ideas? I'd hate to wait till maybe late November and then have a big repair bill when my warranty now would cover it. I'm hesitant to take it to the Ford shop because it works fine now.