Florida's Rainy Season
Florida's waterways, big and small are quickly shrinking as the relentless dry heat of May 2021 drags on. So how long will it last? The short answer is that Rainy Season usually starts in Florida the end of May. But in 2021 it will be delayed by at least a week or two of intense dry heat as relentless high pressure sets up over the Florida peninsula. So expect more weeks of scenes like the one above on Deltona's Lake Theresa and below on Volusia County's Lake George.
Floridian's often wonder when or if we'll get a rainy season as even huge lakes like Lake George (above) start to run dry. For years the rainy seasons have been unpredictable or absent. 2021's spring has been mostly variable. While it is very hot and very dry in late May the National Weather Service is already warning of the potential for summer flooding.
Much drier than normal conditions during January and March across central Florida were offset by increases in rainfall in February and April. May has been completely dry and in late May is turning hot and dry. This has led to overall near to slightly below normal rainfall so far for the year across the region.
The latest three month outlook from the Climate Prediction Center indicates a 33 to 40% chance of above normal precipitation for the months of June, July and August. May will end as it started, hot and dry.
Formula for Finding the Beginning of Rainy Season
It must be noted that a purely objective analysis is not possible because the exact onset of the Wet Season is difficult to determine in some years. There were classic years when dew points and minimum temperatures rose to around 70° in mid/late May, a rainy period ensued shortly thereafter and continued through the summer.
Some years saw the start of showers/storms in late May, followed by several weeks of little/no rain, and then the onset of frequent rains once again in late June. Notably in 1998 neither occurred until late into July. It was in 1998 that much of Central Florida burned in wildfires.
This year dew points and nighttime temperatures are already high but a thermal inversion and semi-permanent high pressure have precluded any rainfall. A series of shortwave troughs are forecast to move through Florida the last week of May which should bring beneficial rains but not what we would consider rainy season rains (from sea breeze thunderstorms).
Attempts to objectively pick the date when dew points/minimum temperatures remained above 70° degrees failed, since many years had brief periods of readings in the 60°s through the month of June. This would have resulted in the median date for the onset of the Wet Season not correlating with a reasonable person's perception, and being much too late in the season.
East central Florida experiences seasons that differ from most of the remainder of the country. Rather than the four seasons of winter, spring, summer and fall, east central Florida exhibits a distinct Wet (warm) Season and Dry (cooler) Season. This duality of seasons is similar to the Monsoon or Wet-Dry climates that other regions of the world experience.
For east central Florida, late February through March might be the time period that most closely resembles typical Spring weather in the higher latitudes. Large swings in temperatures often occur along with occasional severe weather episodes, but rainfall is usually infrequent. April is often the driest month of the year as fronts become weaker and yield less rainfall, yet manage to pass through the area and reinforce the dry and stable air mass. Temperatures warm through May with average maximum readings reaching the upper 80s by the end of the month. Rainfall frequency increases compared to April, with the most notable increase usually beginning late in the month.