A few exceptional days of torrid heat (and wild storms) tempted me to attempt a new heat map of COVID case density in Marin County. Notes: the data are from Marin County HHS and are likely to be undercounting cases, due to the well-established CalRedie system problem. I entered San Quentin with a 10x lower case density than it really had - otherwise the software wouldn’t show any gradations at all for the rest of the county. And all the bright yellow areas - that’s where the county doesn’t provide specific numbers, so I entered plug data (as I did also for Pt. Reyes, where there are known cases, but the zip code population count seems far too low). The white space is atop Mt. Tam, which doesn’t count as being in a zip code at all.