Florida's Rainy Season Getting Underway

One of the more dynamic weather changes in the summer months across the country is now beginning: Florida's rainy season.

Wet Season Begins This Month in Parts of Florida. The period when most of the annual precipitation occurs in Florida is known as the wet season.

The season frequently starts with temperatures in the upper 90s and dry thunderstorms. Miniature thunderstorms produce lightning outside of rainfall and these strikes can create grass fires, especially where the ground is dry following the dry season.

Within a few weeks, this turns into daily thunderstorms across the state.

The forecast is much the same for months at a time: 90-92 degrees, a 50% chance of rain, and humidity levels that make it feel like you could grow gills. But beyond the numbers, the daily forecast changes a lot, too. It may rain multiple times a day, the time the rain will arrive will change and lightning or hail may be more prolific on some days.

(​WATCH: Outdoor Safety Tips To Know Before Storms Hit)

Tampa records about 70% of its average annual rainfall of 46.3 inches during the wet season. Rainy season begins a bit later, usually in early- to mid-June, across central and northern Florida.

Farther south, the rainy season has already begun. Miami gets about 45 inches of rain – almost 75% of its average annual total – from May to October. By late May, the rainy season is usually ramping up across South Florida and it will continue until October.

Florida's Wet Season Setup. With the lack of cold fronts during the summer months, heat and humidity are let loose to bubble up in semi-organized chaos. Thunderstorms often bounce around the state like a really bad game of pinball.

The semi-organized part of this daily phenomenon is related to the driver of the thunderstorms: The sea breeze. As the peninsula heats up each morning and afternoon, this cooling breeze sweeps inland toward the spine of the peninsula. Because the state is surrounded on multiple sides by water, you often get multiple sea breezes that will collide by mid-afternoon somewhere in the middle of the state. Think of this as two cold fronts with embedded clusters of storms colliding into each other.

These sea breezes also put Florida under the bullseye for lightning compared to the rest of the country. Central Florida is often considered the lightning capital of the US.

The purple dashed lines above depict typical sea-breeze boundaries that help to trigger storm formation from late spring into early fall.

But there’s another atmospheric player involved here: A sometimes subtle branch of the Bermuda High. Air flows clockwise around the Bermuda High and it dictates which sea breezes will dominate each day, how strong the thunderstorms will be and which way they'll go later in the day.

For instance, if the Bermuda High sits at home near Bermuda, winds will be out of the southeast during the day (regime 6 or 7 above). This will push the east coast sea breeze toward the northwest, and that collision of the fronts will be closer to Cape Coral and Tampa. In this case, Tampa would receive showers in the morning, then severe thunderstorms late in the afternoon or early evening.

(​MORE: NWS Tampa Bay's Sea Breeze Regime Study)

But thunderstorms bounce, too. Each thunderstorm contains its own miniature cold front called an outflow boundary. When one storm’s boundary collides with another storm’s boundary, that also creates another thunderstorm. This bouncing can go on and on for hours until the day’s heat has dissipated.

If you aren’t with us on this, we're not surprised. It's been said that it takes about 10 summers in Florida to really understand the summer sea breeze and its chaos.

The Great Interruptor: Hurricanes. This daily natural fireworks show goes on until something larger breaks up the pattern. Overlapping with Florida’s rainy season is hurricane season, which officially runs from June 1 through Nov. 30. Hurricanes disrupt this pattern for upwards of a week at a time and have also been known to turn off the rainy season if they near the state in October.

When the tropics get involved, rainfall events go from thunderstorms that last an hour or so to long-winded events that can last much longer.

It's important to remember that a strong hurricane is not needed to bring excessive rainfall; slow-moving tropical storms or even tropical depressions can result in heavy rainfall and flooding in the region.