Covid is naturally persistent in heat because it has evolved to coexist on a bat that generates temperatures above 100 degrees during flight. The horseshoe bat that Covid comes from (Rhinolophidae) generates temperatures of almost 106 degrees Fahrenheit and it persists on the bat without killing it or being killed by it.
I use the word persistence because this is one of the metrics we use to evaluate the effectiveness of chemical and biological weapons-how long does the agent persist once dispersed. Typically, chemical weapon persistence decreases with temperature as heat causes the chemical agent to vaporize and dissipate into the atmosphere. UV radiation and heat are also naturally destructive to most biological organisms. Influenza, for example, has an envelope that hardens like a seed coating in cold temperatures and allows the virus to persist longer on shopping cart handles and such. Covid is not affected like this however, it persists in heat but it does seem to at least be inhibited by heat and UV light because, I hypothesize, it decreases its persistence. But it doesn't stop it and it will evolve to overcome this weakness I suspect.