I thought this was an innovative use for thermochromic pigment.  Basically, it’s painted onto roadways and changes colors according to temperature.  Corresponding signs along the road tell what the coors mean (blue=cold/snow, red/pink=hot).  I think as far as practicality goes, some things need to be worked out.  If the box could give the temperature or have symbols appear in the box in relation to the temperature such as a snowflake for snow or ice and another symbol for extreme heat, it would be more functional.