Since Plato is the percentage weight of sugar in solution and this percentage
doesn't vary with temperature, it isn't necessary to mention temperature
when talking about Plato measurements. However, the specific gravity of
a solution varies with temperature making it necessary (and accurate)
to always specify the temperature when expressing SG. In the absence of
a temperature for a SG reading the standard calibration temperature of
68°F (20°C) can be assumed, however, many of the hydrometers available
to homebrewers are still calibrated to the older 60°F (15.6°C)
standard.
