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Category 5 hurricanes are the most intense, with 1-minute sustained winds of over 155 miles per hour. There is no cutoff for barometric pressure in the eye, but the conventional wisdom is that if a normal-sized hurricane has a pressure of 921 millibars or lower, it probably has Category 5 winds at some place inside it. My own homespun analysis in Microsoft Excel of winds versus pressure suggests a quadratic regression, with pressures falling rapidly after a given wind speed.

Based on meteorological history, I'm inclined to say that the artificial Category 4/5 cutoff is also a good natural cutoff. Many hurricanes have reached 155 mph; a few that come to mind immediately are Floyd of 1999, Georges of 1998, and the Indianola, TX hurricane of 1886. However, it is much rarer for the winds to break this barrier. Until recently, when we entered a new active phase and experienced the beginnings of human-induced atmospheric warming, Category 5 hurricanes were uncommon.

There have been only 29 reliably measured Category 5 hurricanes since 1928, and very few of these made landfall at Category 5 intensity. This page contains detailed information about each storm.

Year Storm Name Dates Maximum estimated winds Minimum barometric pressure
2007FelixAug. 31 - Sep. 5165 mph929 mb
2007DeanAug. 13 - 23165 mph906 mb
2005WilmaOct. 15 - 25185 mph882 mb
2005RitaSep. 17 - 25180 mph895 mb
2005KatrinaAug. 23 - 31175 mph902 mb
2005EmilyJuly 10 - 21160 mph929 mb
2004IvanSep. 2 - 24165 mph910 mb
2003IsabelSep. 6 - 19165 mph915 mb
1998MitchOct. 22 - Nov. 9180 mph905 mb
1992AndrewAug. 16 - 28170 mph922 mb
1989HugoSep. 10 - 25160 mph918 mb
1988GilbertSep. 8 - 20185 mph888 mb
1980AllenJuly 31 - Aug. 11190 mph899 mb
1979DavidAug. 25 - Sep. 8170 mph924 mb
1977AnitaAug. 29 - Sep. 3170 mph926 mb
1971EdithSep. 5 - Sep. 18160 mph943 mb
1969CamilleAug. 14 - 22190 mph905 mb
1967BeulahSep. 5 - Sep. 22160 mph923 mb
1961HattieOct. 27 - Nov. 1160 mph920 mb
1961CarlaSep. 3 - 16170 mph931 mb
1960EthelSep. 14 - Sep. 17160 mphNot available
1960DonnaAug. 29 - Sep. 14160 mph932 mb
1958CleoAug. 11 - Aug. 22160 mph948 mb
1955JanetSep. 21 - 30170 mph914 mb
1951"Easy"Sep. 2 - Sep. 15160 mphNot available
1950"Dog"Aug. 30 - Sep. 17185 mphNot available
1947"Miami Hurricane of 1947"Sep. 4 - Sep. 21160 mphNot available
1938"Great New England Hurricane"Sep. 10 - 22160 mph938 mb
1935"Great Labor Day Hurricane"Aug. 29 - Sep. 10185 mph892 mb
1932"1932 Bahamas Hurricane"Aug. 30 - Sep. 13160 mphNot available
1928"Great Lake Okeechobee Hurricane"Sep. 6 - 20160 mph931 mb
1924"Cuba Hurricane"Oct. 19165 mph910 mb

Special notes:

  1. Pressure reading not available: When a minimum pressure reading is not available for a hurricane, this can have several explanations. For the five hurricanes with this designation, I have given an explanation for each:
    • Hurricane Ethel: According to the National Hurricane Center's "best track" data (1 MB textfile download), Ethel rapidly intensified on September 15, 1960, from a 125-mph Category 3 to a 160-mph Category 5, then back down to a 95-mph Category 1 hurricane. While such wild fluctuations are not impossible -- Hurricane Opal in 1995 did something similar, although not as extreme -- they are definitely weird. The system made landfall near Biloxi, MS, as a tropical storm or minimal hurricane. The only pressure reading associated with the system is a reading of 981 millibars, which, for a Category 5, is impossibly too high. I need to do further research on this storm to determine whether the reading was later considered to be corrupted.
    • Hurricane Easy: This system stayed at sea during the course of its lifetime, and apparently no readings were taken.
    • Hurricane Dog: This system stayed at sea during its lifetime, and apparently no readings were taken.
    • 1947 Miami Hurricane: This system had one pressure reading of 947 millibars taken as it made landfall near Miami as a 150-mph Category 4 hurricane. It was just weakened from Category 5 strength, but no readings are available from when it was a 5. The reading of 947 millibars and 150 miles per hour is reasonable, given that Hurricane Charley in 2004 had a confirmed reading of 954 millibars associated with 145-mph winds.
    • 1932 Bahamas Hurricane: This system did not landfall on the North American coastline, but did hit the Bahamas as a Category 5. However, there are no pressure readings associated with it.

  2. Storms in the 40's, 50's, and early 60's: Some major hurricanes in the 1940's - early 1960's are now believed to have been less intense than recorded. Also, it would be highly unusual for a Category 5 hurricane to have a barometric pressure higher than 930-935 millibars. These facts suggest that several of the storms from that time period listed here were not Category 5. However, this table uses the original, unmodified numbers and will do so until these hurricanes are conclusively reanalyzed. Cleo of 1958 looks questionable to me, and Ethel of 1960 is just bizarre, but I won't make up my own data.

  3. Great Labor Day Storm: No one really knows for sure how fast the winds were in this hurricane. Consider the following:
    • It intensified very rapidly, from a Category 1 to a Category 5 in less than two days, before hitting the Florida Keys, killing hundreds.
    • The Keys were then cut off from the mainland United States in the depths of the Great Depression, because the hurricane destroyed the road and railroad that were under construction.
    • Most instruments were destroyed in the winds and storm surge, and radar had not been invented.
    • It had a confirmed pressure reading of 892 mb from a privately owned barometer in the Florida Keys. It is not known whether this was the lowest pressure from the storm.
    • There were estimates of gusts of "well above 200 mph," per the book Hurricane Watch by Dr. Bob Sheets and Jack Williams (see p. 88), and the book Inside the Hurricane lists an estimate of 250 mph for these gusts. The highest gusts are typically 20 to 25 percent faster than the highest sustained winds: 250 mph / 1.20 = 208.3 mph; 250 mph / 1.25 = 200 mph.
    • The hurricane was very small (an eye of 5 miles); yet the pressure in the eye was extremely low. For a given pressure, the bigger the hurricane, the slower its sustained winds tend to be. Gilbert, with a pressure of 888 millibars and sustained winds of 185 mph, was an enormous storm; this suggests that the 1935 hurricane--being much smaller but having a pressure reading close to Gilbert's--had faster winds than Gilbert. Mitch was also a big storm, and it had a higher pressure than the 1935 hurricane. It is odd that the 1935 storm would have slower winds than Mitch.....
    • ...However, Hurricane Wilma in 2005 was probably the most similar storm of the satellite era to the Great Labor Day Hurricane. It also rapidly intensified from a tropical storm to a Category 5 in less than 24 hours and ended up with a 2-4 nautical mile eye and a barometric pressure of 882 mb, the lowest ever recorded in the Atlantic. After this pinnacle was reached, hurricane hunter aircraft found a pressure of 892 mb (same as the 1935 storm) and 160 mph winds. Wilma had a history of having abnormally low pressures for its winds, though.
    UPDATE: Hopefully there is finally an end to this. NOAA's Hurricane Research Division proposes to change the Best Track file for this hurricane and upgrade its peak wind speed from 160 to 185 mph. Less than I would have made it, by about 10 mph, but still much more reasonable than the barely-Category-5 speed that is in the file as of the 2004 hurricane season revisions.

  4. Hurricane Andrew upgrade: Hurricane Andrew was reanalyzed in 2002 by the Hurricane Research Division of NOAA (see my link page for the URL for their website). Initially it was believed to have made landfall in south Florida as a low-end to middle-range Category 4. However, a reanalysis of the data indicates that it intensified just prior to landfall and hit as a Category 5 with winds of 165 mph. This is not the highest wind speed it achieved during its life span, but is an interesting point.