This is not true. It is based on an extrapolation from other corona viruses that cause the common cold, and "live" primarily in the nose. Nasal tissues are much colder than the rest of the body during the winter. The new corona virus (SARS-CoV-2) infects the throat and the lungs, where it multiplies without any problems at 38 C (100 F).
There is also a study that looked at how long the corona virus survives at different temperatures; here's a snapshot of some results:
- very stable at refrigerator temperature
- stable for days at room temperature
- stable for 6 hours at body temperature
- stable to 5 minutes at 56 C (130 F)
At room temperature, the virus starts to "die" off noticeably within a couple of days. I usually get my mail, put it in the entry room for a couple of days (in a draft-free area), and leave it for 2-3 days before looking at it. Don't forget to wash hands right away after getting mail, and again after opening it!
After writing this post, I found an article from 2011 that looked at another coronavirus: SARS-CoV, the virus that caused the SARS epidemic in 2002-2004. This article looked at how stable SARS is in solution and in dried form. If found that the SARS-CoV was quite stable even in dried form at 33 C (91 F), but not at 38 C (100 F) if the humidity levels were above 95%.
For some other false myths about the coronavirus and weather or temperature, check the WHO website.