Wet vs. Dry U.S. Regions — Precipitation by State

Introduction

This webpage compares wet vs. dry regions in the United States using a 50-state precipitation dataset. The user goal is to quickly see which regions cluster as wetter (ex: Gulf Coast / Southeast) and which cluster as drier (ex: Southwest / Mountain West), and connect that pattern to geography (coasts, mountains, and inland distance).

Key idea: wet and dry states are not randomly scattered — they form regional clusters that match climate patterns.

Average Total Yearly Precipitation by State (50-State Table)

Columns: State, Region label (for geographic comparison), Inches, Millimetres, and Rank (1 = wettest). Sorted wettest → driest.

State	Region	Inches	Millimetres	Rank
Hawaii	Non-Contiguous	63.7	1618	1
Louisiana	Southeast	60.1	1528	2
Mississippi	Southeast	59.0	1499	3
Alabama	Southeast	58.3	1480	4
Florida	Southeast	54.5	1385	5
Tennessee	Southeast	54.2	1376	6
Georgia	Southeast	50.7	1287	7
Arkansas	South/Central	50.6	1284	8
Connecticut	Northeast	50.3	1279	9
North Carolina	Southeast	50.3	1279	10
South Carolina	Southeast	49.8	1264	11
Kentucky	Appalachia	48.9	1242	12
Rhode Island	Northeast	47.9	1218	13
Massachusetts	Northeast	47.7	1211	14
New Jersey	Mid-Atlantic	47.1	1196	15
Delaware	Mid-Atlantic	45.7	1160	16
West Virginia	Appalachia	45.2	1147	17
Maryland	Mid-Atlantic	44.5	1131	18
Virginia	Mid-Atlantic	44.3	1125	19
New Hampshire	Northeast	43.4	1103	20
Pennsylvania	Mid-Atlantic	42.9	1089	21
Vermont	Northeast	42.7	1085	22
Maine	Northeast	42.2	1072	23
Missouri	Midwest	42.2	1071	24
New York	Northeast	41.8	1062	25
Indiana	Midwest	41.7	1060	26
Illinois	Midwest	39.2	996	27
Ohio	Midwest	39.1	993	28
Washington	Pacific West	38.4	976	29
Oklahoma	Great Plains	36.5	927	30
Iowa	Midwest	34.0	864	31
Michigan	Midwest	32.8	833	32
Wisconsin	Upper Midwest	32.6	829	33
Texas	South/Central	28.9	734	34
Kansas	Great Plains	28.9	733	35
Oregon	Pacific West	27.4	695	36
Minnesota	Upper Midwest	27.3	693	37
Nebraska	Great Plains	23.6	599	38
Alaska	Non-Contiguous	22.5	572	39
California	Pacific West	22.2	563	40
South Dakota	Great Plains	20.1	511	41
Idaho	Mountain West	18.9	481	42
North Dakota	Great Plains	17.8	452	43
Colorado	Mountain West	15.9	405	44
Montana	Mountain West	15.3	390	45
New Mexico	Southwest	14.6	370	46
Arizona	Southwest	13.6	345	47
Wyoming	Mountain West	12.9	328	48
Utah	Mountain West	12.2	310	49
Nevada	Southwest	9.5	241	50

Table 1: Average annual precipitation by U.S. state, ordered from wettest (Rank 1) to driest (Rank 50).

Data Analysis

Wettest Cluster (Gulf + Southeast)

The wettest states concentrate in the Gulf Coast and Southeast, where warm ocean air provides moisture for frequent storms and heavier rainfall.

State	Inches	Rank
Hawaii	63.7	1
Louisiana	60.1	2
Mississippi	59.0	3
Alabama	58.3	4
Florida	54.5	5

Driest Cluster (Southwest + Mountain West)

The driest states cluster in the Southwest and interior West. Many are inland and/or affected by deserts and rain shadow effects from mountain ranges.

State	Inches	Rank
Nevada	9.5	50
Utah	12.2	49
Wyoming	12.9	48
Arizona	13.6	47
New Mexico	14.6	46

Conclusion: Sorting wettest → driest makes the regional pattern easy to see: wet states cluster near moisture sources (especially the Gulf Coast), while dry states cluster inland in the Southwest/Mountain West.

Glossary

Precipitation: Water that falls from the atmosphere, including rain and snow (total yearly amount).
Annual Average: A long-term mean value calculated from many years of observations.
Rain Shadow: A dry area on the leeward side of a mountain range where air loses moisture before descending.
Humidity: The amount of water vapor in the air; higher humidity can increase the chance of rainfall.
Latitude: Distance north/south from the equator; influences climate zones and storm tracks.
Coastal Influence: The effect oceans have on climate by providing moisture and moderating temperatures.

Sources

Dataset used for statewide average annual precipitation:
Current Results — Average Annual Precipitation by State