There are plugs (little square boxes that you plug into an outlet) that you can get preset to turn power on when it's below 45 or 30 degrees etc. They also turn power back off at a predetermined temp. I can't remember where to get them, might look in a hardware store. I had one that would turn an electric heater on in a greenhouse when it got below 40, it turned off when the temp got over 45 I think

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1985 300D Turbo ~225k
2000 F350 (Powerstroke) 4X4, SWB, CC, SRW, 6spd ~148k
1999 International 4900, DT466e (250hp/660 ft/lbs), Allison MD3060 ~73k