I wouldn't say it couldn't be plugged, but we're at roughly the same latitude. Assuming it's been in the 20's (F) there, you should be able to let it idle with the heater on high and it shouldn't ever overheat. I start my car 10-20 minutes before I leave home, any time in that range when I get in the ECT reads 150 degrees on the gauge. I usually get to work before the boss gets there to open the shop, and the temp drops back down while I'm sitting there idling. There's a good chance that I'm burning a bit more fuel than you too... unless you have some mods
If the fans do come on, but don't come on when it "overheats", it almost has to be a gauge/sender malfunction. I really think your next step should be to confirm that the ECT is actually high. A low cost alternative to a scan tool is a meat thermometer taped to the upper radiator hose with reflective silver tape... maybe 5 wraps around the thermometer to try to keep some heat in. It will probably read 10-20 degrees cooler than the ECT sensor is, but if it shows 190 degrees and the gauge shows red, you have your answer.