A Monte Carlo method is used to study the propagation of temperature uncertainties into relative humidity with respect to ice (RHi) calculated from specific humidity. For a flat specific humidity distribution and Gaussian temperature uncertainties the resulting RHi distribution drops exponentially at high RHi values-much slower than a Gaussian. This agrees well with the RHi distribution measured by the Microwave Limb Sounder (MLS), which means that such remotely measured RHi distributions can be explained, at least partly, by temperature uncertainties.