The United States contains a vast range of climates, creating significant differences in local weather patterns. To determine which states are truly the wettest, a data-driven approach is necessary. This analysis identifies the top five states that receive the highest total amount of moisture falling from the atmosphere each year.
Defining the Measurement of Precipitation
Determining the “rainiest” state relies on a specific meteorological measurement: the average annual total precipitation. This metric includes all forms of moisture that reach the ground, such as rain, snow, sleet, and hail, with solid forms converted to their liquid equivalent for a standardized total, measured in inches. Weather agencies, like the National Oceanic and Atmospheric Administration (NOAA), calculate these averages over a 30-year period to establish a stable and reliable climate normal. This volume-based measurement is distinct from the frequency of precipitation, meaning a state can have a high annual total without necessarily having the most days with measurable rain.
Ranking the Top 5 Rainiest States
The ranking is based on the sheer volume of moisture received annually, averaged across the entire state.
The state with the fifth-highest precipitation total is Florida, averaging approximately 54.5 inches per year. This total is driven by intense summer thunderstorms and exposure to tropical systems, particularly in the southern and panhandle regions.
Alabama is the fourth rainiest state, averaging about 58.3 inches annually. Its humid subtropical climate and proximity to the Gulf of Mexico ensure high moisture content in the air year-round.
Mississippi holds the third position, recording a state-wide average of around 59.2 inches annually. Its location along the Gulf Coast and the persistent flow of warm, moist air contributes to a high number of heavy rainfall events during the warm season.
Louisiana claims the second spot, averaging roughly 60.1 inches of precipitation each year. The low-lying coastal plain and high humidity make it vulnerable to tropical storm systems that boost the annual totals.
The state that receives the highest average annual precipitation in the US is Hawaii, with a statewide average of approximately 63.7 inches. This figure is heavily skewed by the extraordinarily high rainfall totals in specific, mountainous locations on the islands.
Geographical Factors Behind High Rainfall
The states receiving the highest precipitation totals are largely concentrated in two geographically distinct regions that share a common factor: access to vast sources of moisture. The Gulf Coast states—Louisiana, Mississippi, Alabama, and Florida—draw their moisture primarily from the warm waters of the Gulf of Mexico and the Atlantic Ocean. A persistent atmospheric feature known as the Bermuda High often funnels tropical moisture northward and westward over these states, fueling frequent and intense thunderstorms.
These states are also situated in the path of tropical cyclones and depressions that originate over the Atlantic and the Caribbean, which deliver massive amounts of rain in a short period. Hawaii’s exceptional precipitation is a result of a phenomenon called orographic lift. As steady trade winds carry moist air from the Pacific Ocean, the air is forced upward by the steep slopes of the volcanic mountains. This rapid ascent causes the air to cool, condense, and release its moisture as heavy rainfall on the windward side of the islands.
Regional Variations in US Rainfall
While the rankings identify the states with the greatest volume of precipitation, this does not tell the whole story of a “rainy” climate. Other regions, such as the Pacific Northwest, are often perceived as rainier due to the high frequency of rainy days, even though their annual volume is lower than the Southeast states. Cities like Seattle experience many days of light drizzle, but their total annual inches do not place their states in the top five.
Some northern states and mountainous areas receive significant precipitation in the form of snow, which contributes to the total liquid equivalent. This highlights that a state can be characterized by constant overcast skies or heavy winter snowpack without achieving the nation’s highest liquid precipitation totals.