ET based on PWS and/or interpolation

Not having an option to use PWS to calculate ET is my only disappointment with Rachio. In an area with microclimates, such as the SF bay area, using the closest national weather station can lead to vastly incorrect calculated ET.

@franz mentioned using PWS for ET has its problems; I’m curious what problems are there? Can interpolation or fallback mechanisms help mitigate the problems?

In July 2020, @franz also mentioned in My PWS not showing up that there would be an improvement for ET using interpolation. Has that feature launched? Is the interpolation between national weather stations, or does it factor in the chosen PWS?

Thank you.