The most humid states in the US, ranked by dew point

The pattern the map shows

Two solid blocks dominate the picture, and they are each other's mirror image. A crescent running from the Gulf Coast up the South Atlantic seaboard — Texas and Louisiana through Florida, Georgia and the Carolinas — sits almost entirely in the two most humid bands on the map. Warm ocean water surrounds three sides of it, and the prevailing summer flow pushes that moisture onshore continuously rather than in occasional fronts, which is why the dew point there barely moves week to week.

The second block covers the Mountain West and the Southwest — Nevada, Arizona, Utah, Colorado, New Mexico, Wyoming, Montana and Idaho — and sits almost entirely in the driest band. The mechanism is the opposite of the Gulf's: air crossing the Rockies and the Sierra Nevada sheds most of its moisture as precipitation on the windward side, so what arrives on the lee side has little left to give up, no matter how hot the afternoon gets.

Between those two extremes sits most of the country's population, in a wide middle band that almost never makes a "most humid" or "driest" headline. The mixed-humid climate page covers the practical consequence of living in that band: the same house needs a dehumidifier strategy for its muggiest weeks and a humidifier strategy for its driest ones, because neither extreme description actually fits it for more than part of the year.

There is no sharp line on the map where one block ends and the other begins — dew point falls gradually moving west from the coast, not in a step. The nearest thing to a boundary runs roughly along the edge of the Great Plains, where the last reliable moisture carried up from the Gulf runs out and the rain-shadow effect of the Rockies starts to dominate. States straddling that line, such as Kansas, Nebraska and Oklahoma, post some of the most "average" dew points on the whole table for exactly that reason.

The 10 most humid states

Ten states average a summer dew point of 68 °F or higher: Florida and Louisiana (73 °F), Mississippi, South Carolina and Texas (71 °F), Alabama (70 °F), Arkansas (69 °F), and a three-way tie at 68 °F between Georgia, Hawaii and Virginia. All but Hawaii sit on or near the Gulf of Mexico or the South Atlantic coast, where warm ocean water keeps pumping moisture onshore all summer regardless of how hot or cool any particular day feels.

This is the dew-point band ASHRAE and most people describe as "oppressive" — 69 °F and above. It is also the band where an undersized or short-cycling air conditioner stops being a comfort complaint and starts being a structural one: the AC has to run long enough to actually condense water off the coil, not just satisfy the thermostat, or the house stays clammy at a perfectly cool temperature. Basements and crawl spaces in these states carry the heaviest load, which is why a standalone dehumidifier is closer to standard equipment than an upgrade through most of this list.

Hawaii is the outlier worth a second look — a 68 °F dew point without the sharp, muggy extremes the mainland Gulf Coast gets, because trade winds keep moving the air rather than letting it stagnate over a hot landmass. The number is similar; the lived experience is not, which is exactly the limitation a single statewide average cannot capture.

The practical difference between a 68 °F state and a 73 °F one is smaller than it looks on a ranked list. Both sit well past the point where ventilation alone keeps a house comfortable, and both put basements, crawl spaces and closets at real risk of the musty-smell and mold cycle covered elsewhere on this site. The five-degree spread from Virginia to Florida matters far less to a homeowner's equipment list than the thirty-degree gap between any state on this list and the driest ones below.

The driest states, for comparison

At the other end, ten states average 52 °F or below: Nevada (33 °F) is the clear outlier, followed by Wyoming and Colorado (40 °F), New Mexico (42 °F), Idaho (43 °F), Utah (44 °F), Montana (45 °F), Alaska and Arizona (46 °F), and Washington (52 °F). Eight of those ten are Mountain West or desert Southwest states, where summer air arrives having already lost most of its moisture crossing a mountain range, long before it reaches any city.

A 33 °F summer dew point sounds like winter weather described on the wrong page, but it is simply dry air — comfortable outdoors, and a genuine humidifying problem indoors once it is heated or air-conditioned further. Washington's presence on this list surprises people who associate the Pacific Northwest with rain; Seattle's rain mostly falls outside the June–August window this ranking measures, and marine air at a moderate temperature produces a middling dew point even on a damp-feeling day.

Alaska is a special case rather than a genuinely dry climate — its low dew point comes from being cold, not from holding little moisture relative to what cold air can carry. The same altitude-and-distance effect that dries out the Mountain West states shows up again on the high-altitude climate page, which covers Denver, Salt Lake City and the rest of that band in more detail.

Dry-climate problems indoors look nothing like humid-climate ones, which is worth saying plainly because the same word — "humidity" — covers both. A house in one of these ten states is far more likely to need a humidifier, distilled water to avoid mineral dust, and attention to static shocks and cracked wood joints than to ever see a damp basement. The fix list is close to a mirror image of the Gulf Coast's, equipment and all.

The states that do not make either list

Thirty states fall between the two extremes, with a summer dew point somewhere from 53 °F to 67 °F — noticeably humid by midwestern or northeastern standards, but well short of the Gulf Coast's year-round mugginess. Illinois, Ohio, New York, Pennsylvania and most of the Great Lakes and Mid-Atlantic states sit in this band, along with California, Oregon and most of New England.

This is the largest single group on the map, and the one with the least consistent story: it covers everything from a humid midwestern July to a mild, hazy Boston August, and includes states where the summer problem is real but seasonal rather than year-round. A dehumidifier earns its keep here mainly in a basement or crawl space, and mainly between May and September, which is a different proposition from the Gulf Coast states above, where the equipment runs most of the year.

Why dew point and not relative humidity

Relative humidity answers "how close is this air to saturated at its current temperature." Dew point answers "how much water is actually in this air," independent of temperature. The distinction matters enormously for comparing states: a 55 °F morning in Maine at 90% relative humidity contains far less actual moisture than a 90 °F afternoon in Houston at 55% relative humidity, even though the Maine reading sounds more extreme. Run the two through the dew point calculator and the Maine morning comes out in the mid-50s while the Houston afternoon lands in the low 70s.

This is also why a straight average of relative humidity readings makes cool, cloudy states look artificially humid and hot, sunny states look artificially dry — the opposite of what residents of either place would tell you. Dew point does not have that bias, which is the reason it is the figure building codes and ASHRAE comfort standards use for outdoor humidity, and the reason this ranking leads with it rather than with the percentage.

The same logic explains why this site measures indoor humidity by relative humidity rather than dew point almost everywhere else: indoors, you generally know and control the temperature, so a percentage against that known temperature is the more useful number. Outdoors, across fifty states with wildly different temperatures, the percentage stops being comparable and the absolute figure becomes the only fair one — which is exactly the swap this page makes.

What your state's number means for your house

A state-level dew point is a starting point, not a verdict on any one house. It tells you which season you are fighting and roughly how hard: above about 65 °F, expect a basement or crawl space to need direct dehumidification most summers regardless of how well the air conditioner is sized; below about 45 °F, expect the opposite problem indoors once the heat or the AC runs and strips the little moisture the air arrived with. The full humidity chart turns either number into a room-by-room target.

Large states hide real internal variation that one metro cannot represent. Texas spans four climate zones on its own, from the saturated Gulf Coast to the high desert around El Paso — see the 136-city Texas breakdown for the state-level detail this ranking cannot show. California and New York have similar, if smaller, spreads between their coasts and their interiors.

If your own state sits in the middle of the table rather than at either end, the more useful exercise is reading your own hygrometer through a full year rather than leaning on a single summer average. A state figure tells you what to expect in general; a reading from your own basement, taken in July and again in January, tells you what your actual house is doing about it.