Using Mars Atmosphere and Volatile Evolution observations, we characterize the variability of water vapor in the Martian thermosphere during Mars Years 32-35. Near a fixed atmospheric pressure level of ~5 × 10^-7 Pa, the typical water density is 1.3 (±0.8) × 10³ cm^-3 and the typical water mixing ratio is 10 (±6) ppm. Thermospheric water levels are higher during the southern spring and summer seasons when Mars is near perihelion and there is significant dust loading in the lower atmosphere. However, the seasonal variation is not the same from year-to-year, likely due annual differences in dust loading. Water vapor is highly correlated with lower atmospheric dust, and increases during both regional and global dust storms. Our results support previous work that found increased dust levels allow more water to be supplied directly to the thermosphere.