Where to install flow meter

I see slot of flow meter installs outside
Few inches from ground.
With a new product that has not been proven
With -40 degree C and up to 5 feet of snow how will this survive?
Any harm with putting this inside since There is no back flow ?

  1. Do you blow your lines out at the end of the season?
  2. Isn’t a backflow required by local law?

Flow meters are not new tech.