Links to dew point calculators.
Temperature, Humidity, Dew Point. Enter two and it calculates the third.
http://einstein.atmos.colostate.edu/~mcnoldy/Humidity.html (http://einstein.atmos.colostate.edu/~mcnoldy/Humidity.html)
Notes on this calchttps://www.imagepermanenceinstitute.org/environmental/dew-point-calculator (https://www.imagepermanenceinstitute.org/environmental/dew-point-calculator)
http://www.dpcalc.org/ (http://www.dpcalc.org/)
http://www.decatur.de/javascript/dew/index.html (http://www.decatur.de/javascript/dew/index.html)
EG If the air temp is 66 F and the rel. humidity 32% the dew point is about 35 F according to the first calc. So moisture from the air will condense on a surface that is at 35 F.... cold wall, window, roof, whatever.