The basic wind speed across the Florida Keys grades from roughly 170 mph in the Upper Keys near Key Largo up to approximately 180 mph at Key West. The FBC jurisdictional override status for Monroe is still being verified against current code text — until that confirmation is finished, this page reports the ASCE 7-22 map value.
Calculating wind loads since 2002, online since 2006.
Monroe County stretches from the southern tip of mainland Florida out through 113 miles of low-elevation islands ending at Key West, with no point inside the archipelago more than a few feet above mean sea level. That geography matters: the islands sit inside an open-water hurricane fetch in every direction except due north, and the ASCE 7-22 Figure 26.5-1B contour for Risk Category II reflects that reality with the highest design wind speeds anywhere in the lower 48 states.
Per the ASCE 7-22 map, basic wind speed in the Upper Keys (Key Largo, Tavernier, Plantation Key) runs about 170-172 mph for Risk Category II and grades upward as you move southwest. The Middle Keys (Marathon, Duck Key, Long Key) land near 175 mph. The Lower Keys (Big Pine, Sugarloaf, Cudjoe, Key West) hit roughly 180 mph — the highest contour on the entire map for standard occupancy.
Whether Monroe County publishes an FBC R301.2(7) jurisdictional override that supersedes those ASCE values is something we are still verifying directly against current Florida Building Code text. Until that verification is complete, this page reports the ASCE 7-22 map value rather than guess at an FBC number. The Florida Building Code value, if one exists, would govern over the ASCE map for permit submission — we will publish it here with full citation once confirmed.
Defaults to Key West (33040), the southernmost incorporated city in the continental US. Lower Keys ZIPs (Key West, Big Pine, Marathon) read at the high end of the Monroe wind contour; Upper Keys (Islamorada, Key Largo) drop slightly per the ASCE 7-22 map. No verified FBC override is coded for Monroe yet, so the badge defaults to brand blue with the ASCE citation — we will publish any county override here as soon as verification clears.
The contour gradient from north to south along the Keys is gradual but consistent. Values below are the ASCE 7-22 Figure 26.5-1B map readings for Risk Category II — any FBC override, once verified, will be published in a sixth column.
| City / Island | Primary ZIP | Wind Speed (Cat II) | Position in Keys | Reference |
|---|---|---|---|---|
| Key West | 33040 | ~180 mph (ASCE map, FBC verification pending) | Lower Keys terminus | ASCE 7-22 Fig 26.5-1B |
| Big Pine Key | 33043 | ~178 mph (ASCE map, FBC verification pending) | Lower Keys | ASCE 7-22 Fig 26.5-1B |
| Marathon | 33050 | ~175 mph (ASCE map, FBC verification pending) | Middle Keys | ASCE 7-22 Fig 26.5-1B |
| Islamorada | 33036 | ~172 mph (ASCE map, FBC verification pending) | Upper Keys | ASCE 7-22 Fig 26.5-1B |
| Key Largo | 33037 | ~170 mph (ASCE map, FBC verification pending) | Upper Keys / mainland approach | ASCE 7-22 Fig 26.5-1B |
The 1935 Labor Day Hurricane remains the strongest hurricane ever to make landfall in the United States as measured by barometric pressure: 892 mb at Craig Key on September 2, 1935, with sustained winds estimated at 185 mph and gusts that almost certainly exceeded 200 mph. The storm crossed the Middle Keys as a compact, intensely circulating Category 5 and obliterated essentially everything in its path between Tavernier and Marathon, including the Florida East Coast Railway extension to Key West and the relief camps housing World War I veterans working on the Overseas Highway. The death toll — over 400 confirmed — reshaped American thinking about hurricane evacuation in low-elevation barrier-island geography.
Hurricane Irma made landfall at Cudjoe Key in the Lower Keys on September 10, 2017 as a Category 4 with maximum sustained winds of 130 mph and a central pressure of 931 mb. The eye crossed roughly 25 miles east of Key West before continuing north into the southwest Florida coast and Naples. Damage in the Lower Keys was catastrophic for older single-wide manufactured housing and pre-1992 stick-built homes; structures built or substantially renovated under the Monroe County code post-2010 generally retained envelope integrity and rode out the eyewall passage. Irma is the modern reason every south-Florida insurer scrutinizes Keys housing stock for build year and code compliance.
Between Labor Day 1935 and Irma 2017, the Keys absorbed direct or near-direct hits from Donna (1960, Cat 4 passing Tavernier), Betsy (1965, Cat 3 across the Middle Keys), Georges (1998, Cat 2 from Key West northeast), and Wilma (2005, Cat 3 across the Lower Keys with significant Gulf-side surge into Key West). That landfall density — the highest of any US county for major hurricanes — is what the ASCE map reflects.
Building permits in Monroe County are issued by Monroe County Building Department (covering unincorporated islands), the City of Key West Building Department (Key West proper, Stock Island, parts of Boca Chica), the Village of Islamorada Building Department, the City of Marathon Building Department, the City of Key Colony Beach, and the City of Layton. All apply the Florida Building Code 8th Edition (2023) by adoption, with ASCE 7-22 referenced for wind loads.
Despite carrying the highest ASCE wind speeds in the contiguous US, Monroe County is not part of HVHZ. Florida Building Code Section 1620 limits HVHZ to Miami-Dade and Broward counties only. This catches many designers by surprise: Keys projects use standard Florida Product Approval (FL#) listings rather than Miami-Dade NOAs, and TAS 201/202/203 missile and pressure testing is not jurisdictionally mandated — though most coastal-rated openings and roofing assemblies sold for Keys installation carry the testing voluntarily because the design pressure demands are so high.
The single-road-out evacuation reality — US 1 is the only land route off the island chain — shapes Keys construction culture more than any code provision. Mandatory evacuation orders from Monroe County emergency management typically begin 72+ hours before forecasted landfall because the Overseas Highway can only safely move so many vehicles per hour. Keys homeowners are functionally designing buildings that must survive a major hurricane without occupants present, which is part of why the Lower Keys carry the highest design wind speed in the contiguous US and why post-Irma rebuilds emphasized hardening over restoration.
Basic wind speed: ASCE 7-22 Fig 26.5-1B map value (~170-180 mph Risk Cat II depending on Keys position). FBC R301.2(7) override status pending verification.
HVHZ status: Not HVHZ. Standard FL Product Approval applies.
Code edition: Florida Building Code 8th Edition (2023), ASCE 7-22 by reference
Permitting authorities: Monroe County, City of Key West, Marathon, Islamorada, Key Colony Beach, Layton
Evacuation context: Single-road evacuation via US 1 shapes design assumption that buildings must survive unoccupied.
Calculating wind loads since 2002, online since 2006.