Now for all of you that are going to ask if Global Warming could affect this here is your answer.
Global Warming is projected to alter the global hydrological cycle. A warmer atmosphere will increase global rates of evaporation, shift precipitation patterns, and disrupt water supplies in unpredictable ways, Some areas will get more precipitation and some less. River flows will change. Monsoons and hurricanes are likely to intensify, and the average sea level will rise from thermal expansion of the oceans and partial melting of ice caps and mountain glaciers. The basic problem is that scientists cannot predict precisely when, where, and to what degree such changes will occur.