Predictions of the long-term statistics for rain depolarization are presented for terrestrial path lengths up to 4 km and for any type of linear polarization. Assuming a log normal form for the rain rate statistics, an approximate Gaussian model is deduced for the final cross-polarization isolation (XPI) distribution in decibels. The parameters of the normal distribution are related to the parameters of the radio link and the rain rate distribution. Applications of this conclusion to the estimation of radio outage time due to interference are also presented for various cross-polarization levels.