Flooding can happen anywhere and anytime it rains within or outside of the high-risk zones. Low-risk flood zone does not mean no risk. Over 25% of flood insurance claims come from outside the high-risk areas.
If you are purchasing a home in a high-risk flood area and have a government backed loan, your lender will require flood insurance. The Federal Emergency Management Agency (FEMA) recommends flood insurance for the medium and low-risk areas as well.