Flood Watch, Warning and Advisory Criteria

In Maine, flooding can occur at any time of the year. However, typically, the greatest threat of flooding occurs in the spring when heavy rains and snowmelt can combine to produce excessive runoff. Ice jams can also produce flooding during the late winter and early spring.

To alert the public of these potentially threatening conditions, the National Weather Service issues flood WATCHES and WARNINGS.

FLOOD WATCH is issued when flooding is possible within the next 36 hours.
FLOOD WARNING indicates that flooding is imminent or is currently occurring.

The following are different types of Flood Warnings:

River Flood Warning

Issued specifically for major rivers, these warnings include forecasts of water levels and/or flows at certain points along the river. Widespread heavy rain, possibly coupled with snowmelt, is often responsible for this flooding.

Small River and Stream Flood Warnings

These warnings are issued by county for the smaller rivers and streams. Heavy rainfall, possibly combined with snowmelt, is often responsible for this type of flooding.

Flash Flood Warnings

These warnings are issued by county for rivers and streams when rapid rises in river and stream levels are expected during a short period of time. Heavy, slow moving thunderstorms and dam breaks are often the cause of this type of flooding.

Urban Flood Warnings

Issued for urban areas when local drainage systems are not able to handle the volume of runoff from heavy rain, and possibly snowmelt. In the fall, winter, and spring, leaves or snow may contribute to the flooding by blocking drainage systems.

Coastal Flood Warnings

Issued when the combination of the astronomical tide and the storm surge will result in flooding of coastal areas. Onshore winds associated with large storms contribute to this type of flooding.