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| A distant thunderstorm and a drying lake portend the end of the Florida Dry Season 2022. Lake Theresa's level has dropped over 12-inches in May of 2022. Photo: Phillip Lott |
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The timing and distribution of daily showers and lightning storms during the summer months is most closely tied to the north/south migration of the "Bermuda" high pressure ridge. The position of this ridge controls the low level wind flow and dictates where the Gulf and Atlantic sea breezes collide each day. This collision often produces widespread storms with frequent lightning and heavy rainfall. This dynamic feature of the local climate is referred to as the "Florida Rain Machine." The regularity with which it occurs is also the main reason that the inland area between Tampa and Cape Canaveral is often called the "Lightning Capital of the United States."
Formula for Finding the Beginning
of Rainy Season
Warm Nighttime Temperatures (67-70° F)
+
High Humidities (dew points in the 70°s)
=
Rainy Season
Normally around June 1
Rainy Season Normally ends around October 15
(see more on this below)
While you can usually count on the afternoon clouds building during the summer months, it's a different story during the cooler season in east central Florida. Rainfall is much less frequent, sometimes only occurring a few times during a whole month. This seasonal change is really quite simple to explain. Ask any resident of the state and they will certainly know that the humidity is much lower during the cool season. This lack of moisture is reflected in the virtual absence of the Rain Machine. Rainfall during the cool season is primarily associated with cold and warm fronts that oscillate across the area.
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| Wondering when this relentless heat and dry will end? Soon. Rainy Season 2022 set to begin in earnest by May 20th, a week earlier than climatology. Photo: Lake George, Phillip Lott |
The Rainy Season
So when does this "Rainy Season" begin? Everyone who has lived here or visited here can tell you that it is hot and humid during the summer with frequent showers and lightning storms. Many will be able to tell you that June through September are the wettest months. Climatologically speaking May 27 is the first day of The Rainy Season across Central Florida.
In a classic start to the rainy season, there would be a noticeable return of humidity during the latter part of May. Once this higher humidity (nighttime dew points 70° or higher) arrived, there would usually be an increase of showers and lightning storms within a few days.
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| Lake Theresa Dry Season 2022 Florida had unexpectedly robust rains in Jan and Feb of 2022 which helped to get us through the brutally hot and dry early weeks of May. Photo: Phillip Lott |
2022 has seen an early start to rainy season. This is the 2nd moderate La niña year which may have had some impact on the early start to The Rain Machine in 2022. Around the 20th of May 2022 strong southerly winds are forecast to bring even more moisture north across the peninsula making it feel hotter still and raising rain chances above 50% each afternoon.
There are years when the rainy season onset occurs in early May, or holds off until well into the month of June, or doesn't really appear at all. The highly changeable year of 1998 saw the onset of the true rainy season during the first week of July. When you eliminate the extremes and concentrate on trying to find a typical year, the third or fourth week of May stands out as the most common start for the rainy season.
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| Self-portrait of the photographer Phillip Lott Florida's lakes went into Rainy Season 2022 with a water surplus but levels have dropped rapidly over recent weeks of hot and dry weather. |
The Dry Season
When does the "Dry Season" (or cooler) Season begin? First of all, in order for the frequency of rainfall to decrease, the humidity must decrease. This occurs when a cold front passes through and brings with it some drier air. Many people will recognize this as the first time that they can turn off their air conditioner and open the windows. In most years, this happens by the middle of October.
However, just as the onset of the Rainy Season can be quite fickle, the same can be said for the start of our Dry Season. In many years, the first cool fronts will be short-lived and moisture will return after several dry days. This might lead to a temporary restart of the "Florida Rain Machine." Tropical systems can also result in significant amounts of rainfall throughout October and into November.
So if we get a nice refreshing air mass into the area on the first of October, be wary, because you will usually need those air conditioners again. However, just as winter cold snaps usually last only a few days in the Florida peninsula, the return of humidity during the Dry Season is intermittent and not long lasting.
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| The black waters of Lake Ashby Florida mid-dry season 2022. The lake's cypress forests are largely dry now, awaiting a return of the Florida Rain Machine. Photo: Phillip Lott |
Looking at more than 50 years of temperature and rainfall data from the Daytona Beach and Orlando airports, the median date for the start of the Wet and Dry Seasons was determined. Note that the "median" is simply "the middle of the road." Half of the data is before and half of it is after.
The median date for the beginning of the Rainy Season in Daytona Beach is May 30, while in Orlando it is May 27.
The median date for the beginning of the Dry Season is October 15 for both Daytona Beach and Orlando.
The approximate start of the wet season in Melbourne is May 28, and in Vero Beach it is May 26, while the start of the dry season is October 17.
The approximate start of the wet season in Stuart is May 23, while the start of the dry season is October 22.
Read Randy Lascody's study "The Onset of the Wet and Dry Seasons in East Central Florida: A Subtropical Wet-Dry Climate?" for more detail and to see the data sets that reveal the worst years when the Florida Rain Machine never really got going.
RAINY SEASON DATA
UPDATED THROUGH 2010 REVEAL A
SLIGHTLY LATER START DATE
FOR DAYTONA'S WET SEASON
ORLANDO'S WET SEASON BEGINS MAY 27
Orlando Median Date = May 27
2004
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6/1
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6/3
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2005
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5/30
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5/30
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2006
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6/11
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6/11
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2007
|
6/6
|
6/6
|
2008
|
6/10
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6/9
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2009
|
5/17
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5/17
|
2010
|
5/30
|
5/30
|
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