The diurnal characteristics of various meteorological variables over the island of Taiwan are investigated for disturbed vs. undisturbed periods during the Terrain-influenced Monsoon Rainfall EXperiment (TiMREX), which was conducted from 15 May to 25 June 2008. Data were divided into two categories based on estimated cloud coverage in the morning hours over the island. The diurnal cycles of TRMM rainfall, surface wind pattern, and vertical motion are compared. The results suggest that diurnal cycles in these fields are evident in both periods. However, the overall weather pattern during the undisturbed period indicated a stronger diurnal cycle, with afternoon wind components normal to the coastline 109% stronger than the disturbed period's. The undisturbed period also featured averaged afternoon near-surface vertical motion and convergence almost twice as large as the disturbed period's. Future studies could incorporate sophisticated cloud cover, land surface type, and surface heat flux data to model the influence of cloud cover on the monsoonal weather pattern in Taiwan.