I have some dahlias in our downstairs "cold cellar" (a small narrow room located directly below our outside porch). Today at -10C/14F outside it is 4C/40F in this cellar. (In all the time we have lived here I think the coldest I have ever seen it in that room is 2C/35F)

I've been using one of those 4 area Kalawen weather stations to track temps for a couple of years now. Pretty helpful. I'm a dork and keep a spreadsheet because I do a lot of cuttings and overwintering.

Great "work" @Gawdinfever Z6. This past Fall I purchased waterproof temperature sensors which I can monitor via my phone and can store highs and lows (for the previous 60 days).

Very nice, rouge! I started doing this when I first started getting more serious about propagating. I was paranoid about losing my babies lol. I have a lot of critters that love to dig in my things & knock things over as well. I do cuttings year round, so have a lot in my unheated garage & some warmer zoned plants & many cuttings in my family room under grow lights. Now I can monitor temps in 4 areas while sitting in my office ordering more plants! lol

I had remote sensors in the dark ages. They didn't connect to the computer, but to a monitoring device of their own. The problem was the batteries in the remotes hated cold weather. So they tended to stop working just when things were getting interesting.

My greenhouse is really no warmer than the garden, especially since football playing kids broke a couple of windows... But it is dry and does a good job of preventing plant death from winter rains.

I over most of my hardier tropicals in a minimally heated detached, two car, loft garage (two small oil heaters). It faces due south and get a LOT of winter sun, and we do get a lot of winter sun here.) Used to have a remote temperature monitor to check, but no time anymore. I still overwinter huge Queen palms, Citrus, Cycads, Oleanders, agaves, and other subtropicals. An interesting thing I noticed is that the more the garage is stuffed full of plants, the warmer it gets. Something about thermal mass and physics. It may drop drop down to 27 F on the coldest winter night, but they always pull through the winter.