Original analysis of NOAA, FEMA and Census data

Charleston flood and humidity data

The Charleston Harbor gauge now reaches minor flood stage on about 51.5 days a year, roughly double the 26.3 it averaged over 1992-2020. The air is the other half: about 140 days a year at the airport have an average dew point of 65°F or higher. Here is the record, by year, month and ZIP code.

Every day of 2026 so far at the Charleston Harbor gauge, colored by that day's highest tide. 29 days reached the National Weather Service minor flood stage of 7 feet through September 30, 2026.under 5.5 ft5.5 to 66 to 6.5action 6.5minor flood 7moderate 7.5major 8+NOAA CO-OPS station 8665530, verified high tides. Flood stages: NWS gauge CHTS1.

Days per year the harbor reached minor flood stage (7 ft)

Source: NOAA CO-OPS verified high tides, Charleston station 8665530, counted against the NWS minor flood stage. Years with gaps are left out. 2026 runs through September 30, 2026.

Average days at minor flood stage, by month

Source: NOAA CO-OPS station 8665530, 2016-2025 average. The fall king tides land in September through November.

What we found

Tidal flooding roughly doubled. 26.3 days a year at or above 7 feet over 1992-2020, 51.5 over 2016-2025. The peak year was 2019, with 75 days. Days at the moderate stage of 7.5 feet averaged 14.8 a year over 2016-2025.
Fall is flood season at the gauge. October averages 10.2 days at minor flood stage and September 7.9, when the seasonal high tides line up with fall winds.
2026 so far: 29 days at minor flood stage and 7 at moderate through September 30, 2026.
The highest crests on the National Weather Service list: 12.52 feet in Hurricane Hugo (September 22, 1989), 9.92 feet on September 11, 2017 and 9.86 feet on December 17, 2023.
Muggy most of the warm season. June through September each average 26 to 30 days with a dew point of 65°F or more. The count has stayed in a steady band since 1973, between 108 and 165 a year.
Rain comes in bursts. The airport averaged 53.2 inches a year over 2016-2025. The wettest day on record there was 11.5 inches on October 3, 2015, part of a 15.92 inch three-day total. 2026 has been dry: 28.03 inches through October 27, 2026, against 46.26 in an average year by that date.
Flood claims cluster on the water. 20,687 NFIP claims in the three counties, $337 million paid, an average of $23,575 per paid claim. 12% of paid claims were rated outside the high-risk zones.

Days per year with an average dew point of 65°F or higher

Source: NOAA NCEI Global Summary of the Day, Charleston International Airport (72208013880), 1973 to 2024.

Average outdoor relative humidity by month (%)

Calculated from daily mean temperature and dew point, Charleston International Airport, 2016-2024. Outdoor air, not indoor.

Every day of 2024 at Charleston International Airport, colored by the day's average dew point. 144 days averaged 65°F or higher, the muggy air that keeps a crawl space damp.under 45°F45 to 5455 to 5960 to 6465 to 6970 to 7475+NOAA NCEI Global Summary of the Day, station 72208013880.

Flood insurance claims per year, three Charleston-area counties

Source: OpenFEMA NFIP redacted claims, by year of loss, 1995 to 2026. Hurricane Hugo in 1989 produced 9,591 claims, off this scale.

Highest crests at the harbor

Date	Crest (MLLW)	NWS category
September 22, 1989	12.52 ft	Major
August 11, 1940	10.23 ft	Major
September 11, 2017	9.92 ft	Major
December 17, 2023	9.86 ft	Major
October 8, 2016	9.29 ft	Major
August 30, 2023	9.23 ft	Major
January 1, 1987	8.81 ft	Major
November 24, 2018	8.76 ft	Major
October 27, 2015	8.69 ft	Major
September 4, 1979	8.64 ft	Major

NWS gauge CHTS1 historic crests. Flood stages: action 6.5 ft, minor 7, moderate 7.5, major 8.

The Ravenel Bridge over the Cooper River at sunset, seen from Mount Pleasant — The Ravenel Bridge from Mount Pleasant. The harbor gauge that measures tidal flooding sits just downstream. Photo: David Martin / Unsplash

Flood claims and housing by ZIP code

Ground height is the USGS elevation at the Census center point of each ZIP code, so it describes one spot, not the whole ZIP. Use it as a rough guide to how low an area sits.

ZIP	Area	NFIP claims	Since 2015	Paid	Ground at center	Median year built	Built before 1980	Renter occupied	Homes
29401	Downtown Charleston	3,215	1,335	$78,434,925	12 ft	1938	69%	40%	5,754
29451	Isle of Palms	2,691	261	$65,743,600	0.5 ft	1986	17%	7%	4,674
29412	James Island	2,454	825	$22,880,512	8.4 ft	1990	27%	27%	18,413
29407	West Ashley	2,261	836	$26,087,908	13.5 ft	1971	48%	43%	18,907
29464	Mount Pleasant	1,783	290	$19,677,296	18.5 ft	1992	11%	35%	27,269
29439	Folly Beach	1,213	202	$17,553,779	2.4 ft	1990	28%	6%	2,022
29414	West Ashley (Bees Ferry)	1,210	744	$18,907,836	18.1 ft	2001	10%	38%	20,424
29455	Johns Island and Kiawah	1,026	513	$4,205,176	1.3 ft	2001	7%	12%	17,781
29403	Upper Peninsula	995	308	$9,214,186	2.3 ft	1964	55%	67%	13,460
29482	Sullivan's Island	894	82	$22,220,092	1.7 ft	1981	41%	15%	1,088
29405	North Charleston	325	173	$3,458,203	24.8 ft	1964	60%	49%	13,393
29485	Summerville (Dorchester)	320	275	$7,021,043	22.9 ft	2001	5%	26%	23,602
29418	North Charleston	278	105	$3,575,875	21.3 ft	1988	13%	45%	12,448
29410	Hanahan	248	151	$3,422,336	8.3 ft	1986	27%	32%	8,671
29456	Ladson	205	163	$5,010,317	47.2 ft	2004	6%	38%	16,739
29466	Mount Pleasant (north)	205	96	$2,403,487	13.4 ft	2007	2%	15%	18,639
29406	North Charleston	194	103	$5,532,835	25.9 ft	1991	19%	58%	14,548
29445	Goose Creek	120	88	$979,144	26.1 ft	1991	12%	28%	23,099
29483	Summerville	119	90	$1,702,414	51.8 ft	2002	11%	21%	23,728
29461	Moncks Corner	103	88	$1,969,342	44.3 ft	2001	11%	18%	16,715
29449	Hollywood and Meggett	83	59	$634,561	12.7 ft	1995	12%	14%	3,769
29429	Awendaw	82	22	$3,227,584	4.6 ft	2007	13%	6%	1,819
29420	North Charleston (Dorchester)	71	65	$2,767,686	25.1 ft	1999	7%	38%	9,957
29492	Daniel Island and Cainhoy	44	33	$196,336	3.8 ft	2011	1%	40%	10,531
29487	Wadmalaw Island	30	14	$60,104	13.2 ft	1991	20%	6%	1,354
29486	Summerville (Nexton)	21	20	$266,952	63.3 ft	2012	1%	22%	21,508
29470	Ravenel	19	13	$272,763	33.1 ft	1997	17%	13%	2,262

OpenFEMA FIMA NFIP redacted claims by reported ZIP code, all years. Census ACS 2020-2024 5-year estimates by ZIP Code Tabulation Area (B25001, B25003, B25034, B25035). USGS 3DEP elevation. Click a column to sort.

Federal disaster declarations for storms and floods

Incident began	Event	Type	Counties
January 21, 2026	Severe Winter Storm	Emergency	Charleston, Berkeley, Dorchester
September 25, 2024	Hurricane Helene	Major disaster	Berkeley
August 4, 2024	Tropical Storm Debby	Major disaster	Berkeley, Dorchester
August 29, 2023	Hurricane Idalia	Emergency	Charleston, Berkeley, Dorchester
September 25, 2022	Hurricane Ian	Major disaster	Charleston, Berkeley, Dorchester
April 12, 2020	Severe Storms, Tornadoes, And Straight-Line Winds	Major disaster	Berkeley
August 31, 2019	Hurricane Dorian	Major disaster	Charleston, Berkeley, Dorchester
September 8, 2018	Hurricane Florence	Major disaster	Charleston, Berkeley, Dorchester
September 6, 2017	Hurricane Irma	Major disaster	Charleston, Berkeley, Dorchester
October 4, 2016	Hurricane Matthew	Major disaster	Charleston, Berkeley, Dorchester
October 1, 2015	Severe Storms And Flooding	Major disaster	Charleston, Berkeley, Dorchester
February 10, 2014	Severe Winter Storm	Major disaster	Berkeley, Dorchester
August 29, 2005	Hurricane Katrina Evacuation	Emergency	Charleston, Berkeley, Dorchester
September 6, 2004	Tropical Storm Frances	Major disaster	Charleston, Berkeley
August 28, 2004	Tropical Storm Gaston	Major disaster	Charleston, Berkeley
January 22, 2000	Severe Winter Storm	Major disaster	Charleston, Berkeley, Dorchester
September 14, 1999	Hurricane Floyd	Major disaster	Charleston, Berkeley, Dorchester
September 21, 1989	Hurricane Hugo	Major disaster	Charleston, Berkeley, Dorchester

OpenFEMA Disaster Declarations Summaries, Charleston, Berkeley and Dorchester counties, hurricanes, storms and floods.

How we built this

Tides. Every verified high tide at NOAA CO-OPS station 8665530 (Charleston, Cooper River Entrance) from 1980 on, in feet above mean lower low water. A day counts when its highest tide reached the National Weather Service flood stage for gauge CHTS1: minor 7 feet, moderate 7.5, major 8. Years with large gaps are left out, which leaves 44. NOAA publishes its own high tide flooding counts using a different, national threshold, so its numbers are lower than ours.

Humidity. NOAA NCEI Global Summary of the Day for Charleston International Airport (72208013880), daily mean dew point, 1973 to 2025. Relative humidity is our calculation from the daily mean temperature and dew point.

Rain. Daily precipitation at Charleston International Airport (GHCN USW00013880) via NOAA's Applied Climate Information System, 1938 to October 27, 2026.

Claims and housing. OpenFEMA FIMA NFIP redacted claims and disaster declarations for Charleston, Berkeley and Dorchester counties. US Census ACS 2020-2024 5-year estimates by ZIP Code Tabulation Area. The NFIP data covers flood insurance only; most water damage inside homes comes from leaks and is never in it.

Limits. One tide gauge and one airport don't describe every street. Flooding in a given neighborhood depends on drainage, elevation and rain as much as the harbor level. Use this to understand the area, not to judge a particular house.

Using this data. Journalists and inspectors are welcome to cite or republish these charts and tables with a link to this page (CC BY 4.0).