Internet constantly dropping in cold temperatures

I'm having an issue where my internet keeps dropping when temps fall below 15-20 degrees Fahrenheit. Its definitely cold weather related as the minute temps drop below 15-20 degrees, the issues start again. Had a cold stretch a few weeks ago and had a tech come out. Initially insisted it was my Netgear modem. I had already ruled that out since I bought a new modem and was having the same issues. However he still insisted that was the issue because he was "seeing good signal" at the modem outlet. Went to his truck and got an Xfinity gateway and set it up and had it added to my account. Still didn't work, so he insisted that Xfinity gateway must be bad also and went and got another one.  Still did not fix the problem and ended up checking all connections entering house and replacing a splitter in the basement where the service entered the house.  Still not fixed. Came out the next day and ran a new cable from the pedestal to the house.  By that time, the weather had warmed up above 20 degrees and the internet drops stopped. The next day temps dipped again and the drops came back.  

Although the tech "sees good signal" with his equipment, when I log into the modem I see that I'm losing downstream channels (multiple channels not locked) as well as I'm seeing SNR levels changing up to 4 or 5 dB on the same channel within a minute. Power levels are generally more stable even when SNR dB jumps. There are also a lot of Uncorrectables.  Power levels on each downstream channel range from about -3 dBmV to 0 dBmV. SNR levels range from 31.5 dB to 37 dB but all fluctuating.

Any thoughts on what could be causing this? I'm assuming it has to be an issue with an upstream device (tap, etc.) but its extremely difficult to 1) be able to even talk to an agent and not get stuck in an Xfinity Assistant AI loop and 2) convince them the problem isn't in my house or with my equipment without having to 'troubleshoot' everything all over again and again. I reached out to the previous tech the day after he was here when the issues started up again when temps dropped and he was going to escalate to his supervisor, but then I never heard another word and stopped getting responses. That was a few weeks ago and temps have been warm enough that I haven't had any drops until today again.