The hydrologic cycle in the Keys is not constant. Total and monthly rainfall vary considerably from year to year. The daily heat budget and hydrologic cycle are influenced by the vast wetlands of south Florida. Land development such as urbanization and wetland drainage may be inadvertently modifying local weather patterns by redistributing rainfall via changes in the overall daily heat budget.

The removal of wetlands from the weather cycle through paving and other urban development magnifies the shift toward higher temperatures. The cumulative effects of development and drainage may be slowly replacing Florida’s wet season "rain machine" with a relatively drier "heat machine" during the summer months. Consequently, wet season rains so essential to south Florida’s ecosystems may be occurring less frequently due to massive changes in the daily heat budget brought on by large-scale destruction of south Florida wetlands.