2021-8-6 · Weather Charts: New Covid-19 forecasts: Per the US DHS, the half-life of the SARS-CoV-2 virus in open air is inversely correlated to UV radiation, relative humidity, and temperature oose those graphs below for a rough estimate. UV radiation (sunlight) matters a lot (high UV is good), relative humidity and temperature matter less, but for both, high values are good.