We had my Chrony and a bud's ProChrono side-by-side yesterday in drizzle/overcast, under a canopy. Neither would read. The Chrony showed "error", the Pro showed nothing. I've had hit-n-miss luck under a canopy, depending on ambient light.
When removed from the canopy, they still wouldn't work. My bud has a piece of plexiglass that he made as a rain shield. We eventually got some readings but the water droplets caused some weird results. And fog under the shield.
I need a box with opaque top...
