Unseasonably deep tropical moisture persisted across Martin and St. Lucie counties for nearly four days, just to the north of a stationary front. A secondary front then dropped south and stalled across Martin and St. Lucie counties. Moderate onshore flow within the moist air mass, combined with favorable conditions aloft, and resulted in development of several periods of heavy rain along the coast, with training of shower bands. Multi-hour rain rates of 1-to-3-inches-per-hour occurred during three seperate periods between the early morning hours of October 1 and late afternoon of October 3.
Much of this same area was impacted by flash flooding during the early summer and the local water table remained very shallow, resulting in renewed flooding. Numerous roadways became impassable, drainage culverts were overwhelmed, standing water reached three feet or more in some neighborhoods and water entered several homes.
The most significant (flash) flooding affected portions of Martin County (primarily Hobe Sound, Port Salerno and Sewall's Point) on October 1 and 2. Considerable flooding of roadways, drainage canals and yards affected St. Lucie County (primarily Lakewood Park and the southern portion of Ft. Pierce), mainly on October 3.

Flash Flood in MARTIN, FLORIDA
From 01-OCT-20 02:30:00 to 01-OCT-20 05:30:00 (EST-5)
Location: GOMEZ
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Between 5 and 8 inches of rain fell during the early morning hours, within an area with a shallow water table due to previous heavy rainfall. Showers moved onshore or developed along the coast and trained over areas south of Port Salerno, impacting Hobe Sound most significantly, and in particular Hobe Heights. Rapid inundation occurred, with standing flood waters exceeding a depth of 3 feet in portions of Hobe Heights and surrounding neighborhoods, where flood waters approached homes, overtopped culverts and creeks and caused dozens of roads to become fully or partially impassable. The flood waters were very slow to recede.

Flash Flood in MARTIN, FLORIDA
From 02-OCT-20 12:00:00 to 02-OCT-20 15:00:00 (EST-5)
Location: STUART WITHAM FLD
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Training bands of heavy showers redeveloped across coastal areas of Martin County during the morning of October 2 and persisted into the early afternoon. Rain totals of 5 to 8 inches fell across the same area impacted by 6 to 10 inches only a day earlier. Many of the same areas which experienced flash flooding were again inundated with rapidly rising water, exceeding 3 feet in some areas. High water resulted in the closing of dozens of roadways. Flood waters approached many homes and intruded into several homes resulting in damage. Drainage canals and creeks overflowed and high water from the Savannas Preserve flowed into surrounding areas. The flood waters were very slow to recede.

Heavy Rain in MARTIN, FLORIDA
From 01-OCT-20 00:00:00 to 04-OCT-20 19:00:00 (EST-5)
Location: STUART
Reported by: Mesonet

CoCoRaHS, mesonet and Cooperative observer reports, along with reports from SKYWARN spotters and Emergency Management officials indicated that rainfall totals reached ten to over twenty inches between the early morning hours of October 1 and the early evening of October 4. Observations over twelve inches were received from seven recording stations within Hobe Sound and Stuart (highest value was from a Weather Underground mesonet site in Stuart; 20.63 inches).

Heavy Rain in ST. LUCIE, FLORIDA
From 01-OCT-20 00:00:00 to 04-OCT-20 19:00:00 (EST-5)
Location: EDEN
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

CoCoRaHS, mesonet and Cooperative observer reports, along with reports from SKYWARN spotters and Emergency Management officials indicated that rainfall totals reached eight to nearly fifteen inches between the early morning hours of October 1 and the early evening of October 4. Observations over twelve inches were received from three recording stations within Jensen Beach, Port St. Lucie and Fort Pierce (highest value was from a Weather Underground mesonet site in Ft. Pierce; 14.88 inches).