Following a July that saw well below average precipitation fall across South Florida, August more than made up for any deficit. Rainfall associated with Hermine – the state’s first land-falling hurricane in 11 years — led to above average totals for the region.
More than 9 inches of rain fell across the South Florida Water Management District (SFWMD), representing 113% of average, or 1.06 inches above average. The wettest parts of SFWMD’s 16-county region were the Water Conservation Areas, Big Cypress National Preserve, and the eastern urban areas of Broward and Miami-Dade counties. Those basins received between 121% and 171% of their average rainfall for August.
Areas of the peninsula most impacted by Hermine’s effects (west and northwest) experienced flooding conditions. More than 20 inches of rain was recorded in the Tampa area, according to reports.
In response to the heavy rains from Hermine, the Southwest Florida Water Management District activated the Tampa Bypass Canal system.
The Hillsborough River reached an elevation of 25 feet above sea level, which triggers the Army Corps of Engineers activation level of the Lower Hillsborough Flood Detention (LHFDA) area. This involves redirecting the entire flow of the Hillsborough River away from the City of Temple Terrace and City or Tampa into the LHFDA, which will assist with flooding from the Hillsborough River in Temple Terrace and the City of Tampa.
Since last November, South Florida has experienced unprecedented rainfall Districtwide. The period between November 2015 and the end of August has been the second wettest since the District was created in 1949. The average annual rainfall for 12 months is approximately 52 inches. In the 10 months since November, 52.54 inches of rain have already fallen.
In particular, the SFWMD has experienced 10 “big rain days,” defined as a day with more than 1 inch of rainfall, so far this year. That ties 1995 for the most big rain days. The District typically averages 5.5 such days per year.