The lowest sea-level pressure ever recorded 870 millibars (or 25.69 inches of mercury) in the storm Typhoon Tip. It was recorded 300 miles west of the island of Guam in the Pacific Ocean at latitude 16 deg 44 min north, longitude 137 deg 46 min east, on Oct. 12, 1979.  A hurricane hunter plane flying through the Category 5 storm's eye of Wilma, on October 19th of 2005 found a minimum central pressure of 882 millibars, this would be an all-time record for an Atlantic storm surpassing the record set in 1988 by Gilbert which was 888 millibars (mb). 
A detailed report on Wilma can be found at   An archive of Wilma radar loops can be found  at (scroll down to Hurricane Wilma 2005).

The standard WMO threshold limit for reduction to sea level pressure is at 750 meters; however, recently the World Meteorological Organization (WMO) has created two categories for record station pressures: (1) one at stations below 750 meters; and (2) a second one for stations above 750 meters.

For Stations Below 750 meters
The accepted world record maximum "sea-level equivalent" pressure for stations below 750 meters was observed at Agata Lake (66 degrees 53 minutes N; 93 degrees 28 minutes E) in Siberia at 1200 GMT on 13 December 1968: that record is 1083.8 mb (32.00 inches) as noted on the site at The station elevation is 263 meters; the temperature was -46 degrees C. Extraordinarily high surface pressures observed nearby at the same time corroborated the record measurement.  Seven stations recorded pressures in excess of 1070 mb, indicating that the pressure at Agata was in keeping with the general situation over the area. 

For Stations Above 750 meters
The accepted world record maximum "sea-level equivalent" pressure for stations above 750 meters was observed at Tosontsengel, Mongolia (48 degrees 44 minutes North; 98 degrees 16 minutes East) on 18 December 2001 (2:00 am local time on the 19th). Using the supplied station pressure of 845.9 hPa, a geopotential height of 1725.8 m, and an ambient air temperature of -42ÂșC, the WMO method for reduction to sea level pressure produces an adjusted sea level pressure value was 1084.8 mb (32.03 inches) as noted on the site at The formula used is given in WMO Techn. Note No. 61, page 22, eq. 2).

The North American record for high pressure was set in 1989. At 2000 GMT on 31 January 1989, an anticyclone of historic proportions brought a "sea-level equivalent" pressure of 31.85 in (1078.4 mb) to Northway, on the Alaska Highway in the east central part of Alaska. When pressures occur in this range, many commercial aircraft are grounded because their altimeters aren't designed for such high settings.