May 1st marks the start of a new "water year" in south Florida.
|The animation above shows the difference|
between the calendar and water year. Blue labeled
boxes are reliably rainy months, yellow reliably
dry and green for months that could
go either way.
South Florida's water table typically bottoms out in May.
May also marks the start of the 5-6 rainy month stretch.
In terms of hydrologic book keeping, May 1st makes a lot of sense.