Water ice is strongly implicated as the major component of polar mesospheric clouds (PMC), noctilucent clouds (NLC), and possibly polar mesospheric summer echo (PMSE) layers. Hervig et al [2001] have recently shown the infrared spectral signatures of water ice in HALOE solar occultation observations in suspected PMC layers. We have taken a complementary approach by seeking evidence that ice can form in these locations. Ten years of UARS-HALOE temperature and water vapor data are used to investigate ice saturation at the summer, high latitude mesopause. The saturation computed from individual profiles reveals that regions of supersaturation occur precisely where satellite observations of PMC tend to occur in latitude, altitude, and day of the year. This appears to be the first time that such comparisons have been made for a near-global data set, including both northern and southern hemispheres. Finally, there is slightly less water vapor and somewhat lower ice saturation in the PMC region in the SH compared to the same region of the NH.