Corky,

With knowledge of the surface temperature, dewpoint, and lapse rate a
pilot can make an educated guess at what altitude cloud bases are
likely to be. Also, with knowledge of the temperature at your altitude
and lapse rate you can estimate your proximity to the freezing level.
Granted, lapse rates vary greatly and these "calculations" are more
like ballpark guesses, but they're still valuable.

Regards,

Rob