Humidity and temperature considerations
What you describe doesn't sound like much of a problem.  Even if you mean 4 &deg;C, there is very little moisture in the air, especially at 50% RH.  Any electronics will dissipate some heat, so the board should be slightly warmer than the air.  Even if it were the same temperature, I don't see why you expect condensation.

Basically 4 &deg;C and 50% RH shouldn't be a problem.