Boomtown: Thunder, Lightning Rule

LAKELAND | The boom of thunder was heard in Lakeland on 14 days during July, a month that produced 9.12 inches of rain, which is 1.61 inches more than normal.

That's simply the way it is in "Lightning Alley," the area extending from Tampa to Titusville. With an average of 100 to 120 thunderstorm days a year, the area leads the U.S. in the number of lightning strikes - and the number of deaths.

Ninety percent of the thunderstorms in Central Florida occur from June through October, putting us right in the middle of lightning season.

July was a prime example as thunderstorms boomed across the county. Total rainfall at Lakeland Linder Regional Airport was 9.12 inches, but the Division of Forestry recorded 15.9 inches in Dundee, 9 inches at its office on U.S. 98 in the Green Swamp, 8.15 inches in Polk City and 10.2 inches at the Lake Wales Ridge State Forest.

At this time of year, it's all about location. Hot air rises over the interior of Central Florida, generating sea breezes to replace it. Where those sea breezes from the two coasts collide, often over Polk County, the worst thunderstorms often form, according to the National Weather Service. The result is a summer forecast that includes an almost daily chance of thunderstorms.

The thunderstorms build, unload their moisture, dissipate and reform. It can come down in buckets in one area and be dry a mile away, which is why rainfall totals vary greatly in Polk.

A single thunderstorm typically generates about 200 cloud-to-ground lightning strikes, according to Charlie Paxton of the National Weather Service. But "more vigorous storms" can generate about 3,000 strikes.

It all adds up to about 10,000 strikes a day over Central Florida.

From 1997 to 2006, there were 71 deaths caused by lightning in Florida, compared with 30 in Colorado, 25 in Texas, 21 in Georgia and 19 in North Carolina.

Since 1959, lightning has killed 25 people in Polk County, but there have been no deaths in the county since 2005.

In Florida, 11 people died last year and two have been killed so far this year. While flooding is the leading weather-related cause of death nationally, in Florida lightning causes more deaths than any other weather phenomenon, according to the National Weather Service.

To avoid injury, officials say the best bet is to simply seek shelter. If the interval between the lightning flash and the thunder is five seconds, the lightning strike is about a mile away. If the lightning is within six miles (30 seconds), you are in danger and will be for about 30 minutes, according to the National Weather Service.

Lightning is 50,000 degrees - three to five times as hot as the surface of the sun - carries 100 million to a billion volts and occurs annually about 22 million times in Florida. A single bolt contains 100 million to 1 billion volts of electricity and 10,000 to 200,000 amps. The average bolt would light a 100-watt bulb for three months.

More lightning can be expected during the next few days, although the rainfall chance is down slightly to 40 percent through Monday, according to Paxton. Until the rainy season ends, usually in late September or early October, Central Florida residents can expect similar forecasts, although the chance of rain on any given day may vary.

But those thunderstorms have already raised lake levels and groundwater tables. According to the Southwest Florida Water Management District, groundwater tables are in the normal range for this time of year. Lake levels remain below normal, but are rising. The flow of the Peace River at Bartow is approaching the normal range.

The Winter Haven Chain of Lakes rose about 16 inches during July and most canals connecting the lakes are again navigable for average-sized boats, said Roger Griffiths, executive director of the Lake Region Lakes Management District.

"We did not expect the lakes to come up that fast," Griffiths said. However, he said the chain remains about two feet below optimum levels.

There was one record set in July. The 2.68 inches recorded on July 17 in Lakeland broke the previous record for the date of 2.26 inches, which had stood since 1949.

The wettest July ever was in 1960, when 15.67 inches was recorded. The driest was in 1961, with 3.09 inches.