A combination of satellite observations is used to study the global variation of polar mesospheric cloud (PMC) brightness and to determine its correlation with transient mesospheric dynamics. The observations include the PMC database from the Student Nitric Oxide Explorer (SNOE) satellite and measurements of atmospheric temperature made by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument onboard the Thermosphere-Ionosphere-Mesosphere-Energetics and Dynamics (TIMED) spacecraft. The analysis is unique in that we have contemporaneous measurements of PMCs by SNOE and atmospheric temperature by SABER for three summer mesosphere seasons (two northern, in 2002 and 2003; one southern, 2002–2003). The results show the presence of planetary wave activity in both PMCs and mesospheric temperature that are strongly coherent with each other. The dominant waves present in the polar summer mesosphere are the 5-day wave number 1 and the 2-day wave number 2 Rossby normal modes. The maximum amplitude of the temperature perturbations is small (2.0–3.5 K) but has a significant effect on the PMC brightness. The SABER temperature amplitude in the southern season is slightly larger than the northern seasons for both planetary waves with a corresponding increase in PMC planetary wave activity. The phase relationship between temperature and PMCs indicates that they are very close to 180° out of phase (cold temperatures coincide with bright PMC). This analysis establishes the importance of temperature as a forcing mechanism for planetary-scale variability in PMCs.