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Frequencies from flooding associated with rain events other than tropical storms and hurricanes are more difficult to estimate . Eastern Florida shows an annual dry cycle stretching from early November through mid - May . During this part of the year , monthly rainfall rarely exceeds 3 . 5 to 4 . 0 inches per month . The wet season , beginning in mid - May and running through late October, shows monthly rainfall levels in the area to a 6 . 0 to 8 . 5 inches . Heaviest rainfall usually occurs in June and September. In Indian River County , the eastern or coastal section of the County receives more rain than the western section . The average annual rainfall in Indian River County ranges between 50 and 55 inches . The County sees its maximum monthly rainfall in September, and its minimal rainf II in January. This rainfall pattern coupled with the hurricane season (June through November) makes Indian River County particularly vulnerable to flooding associated with tropical storms and hurricanes because they typically occur when the water table is high and the ground is saturated . The County' s Flood Insurance Study , dated 4 May 1989 , identified the following sources of flooding within the County: • Sebastian Creek ; • South Prong Creek ; • St. Johns River; • Elkcam Waterway — Collier Waterway ; • Lateral G ; • Lateral H ; • Lateral J ; • North Relief Canal ; • South Relief Canal ; • Main Relief Canal ; and • Vero Lakes Channels A , B , C , and D . The East Indian River County Master Stormwater Management Plan also identified the following flood zones within the County : North Relief Canal Sub basin , Main Relief Canal Sub- basin , and South Relief Canal Sub - basin . North Relief Canal Sub-Basin . The second largest areas of flooding within the Indian River Farms Water Control District ( IRFWCD ) is within the North Relief Canal Sub-basin C- 1 . The boundaries are as follows : 65th Street to the north , 66th Avenue to the east , 74th Avenue to the west , and 45th Street to the south . The flood elevations range from 22 to 23 feet. Another flood prone area is located along the Lateral " G " Cana , 1 /4 mile wide from 85th Street to 65th Street. Flood elevations range from 19 to 23 feet sout i to north , in this area . Furthermore , an area connected to the North Relief Canal by the L ateral " H " Canal is subject to flooding . This designated zone is bounded by 45th Street on the north , 28th Avenue on the east , 35th Avenue on the west , and 41 st Street on the sout i . Flood elevations are between 21 and 22 feet. The flood prone areas of the northerr basin will be addressed in detail in a subsequent phase of the Stormwater Master Plan ( Indian River County Public Works , 2002 ) . Main Relief Canal Sub-Basin. According to the 1988 Storm Water Management Model , the largest area of flooding within the Main Relief Canal Sub- basin during a 10-year storm event is connected to the Indian River Lagoon by both the Main and South Relief *4W Canal The approximate boundaries of this flood prone area are as follows : he Main Relief Canal to the north , 43rd Avenue to the east , and 74th Avenue to the west . The other flood 4- 16