wunderground.com, as data

*METARS chart for Appleton, Wisconsin on July 13, 1995 from wunderground.com.*The July 1995 heat wave resulted in the deaths of 750 people in Chicago and other cities in the region recorded amazing dew points as well such as Cedar Rapids, Iowa: 84° (heat index 129°) and Oelwein, Iowa 85° (heat index 131°). Unusually high dew points in the region persisted for a couple days, aided by evaporation from soil and a stable layer of air aloft that prevented moist air in the lowest few thousand feet from mixing with drier air above. This was also the case in Minnesota and North Dakota last month on July 19th.Aside from Appleton, the only other instances of 90° or higher dew points I am aware of are the following: 91° at Melbourne, Florida at 2 p.m. on July 12, 1987 (air temperature 95°) and 90° at New Orleans Naval Air Station at 5 p.m. on July 30, 1987 (air temperature 91°). Both of these records have not been vetted for accuracy.Record high dew points seem to be a particularly difficult record to verify. On the East Coast I can find no reference to what New York City’s highest dew point might have been. Philadelphia’s highest such was 82° on July 15, 1995 (the heat index peaked at 129°). Syracuse, New York’s record was 77° on July 4, 1999. Anecdotal on-line reports claim an 86° dew point at Virginia Beach, Virginia sometime during the summer of 1998. In general, it may be assumed that the highest dew points on record for most places east of the Great Plains would be in the 77°-85° range.**Highest Dew Point Levels in The World**The hottest most humid regions of the world are the coastal areas of The Persian Gulf, Red Sea, and Gulf of Aden.*Map of the Arabian Peninsula region, the coastal areas of which record the highest dew points in the world. Boosaso (referenced below) is located on the Gulf of Aden coast of Somalia just visible at the bottom portion of the map. Dhahran, Saudi Arabia is located on the Persian Gulf just north of Bahrain.*Thanks to the shallow nature of these bodies of water they heat up during the summer season with average sea surface temperatures in the upper 80°s. In fact, the hottest sea surface temperatures ever recorded anywhere in the world have been 98° in the Persian Gulf and 96° in the Red Sea. Data compiled by the British Met Office (in its ‘Tables of Temperature, Relative, Humidity and Precipitation for the World: Part 4; Africa and the Indian Ocean’, 1967) for Boosaso (formerly known as Bender Caasim), Somalia between 1934-1946 indicate an *average* dew point of 83° at 2:30 p.m. during the entire month of June (104° air temperature with 61% humidity). Obviously, some days are even hotter and more humid (the record June high for the period was 113° and the record low 78°). Assab, Eritrea has an average June afternoon dew point of 84°.The absolute highest dew point recorded in the region and therefore the world (of which I am aware) was 95° at Dhahran, Saudi Arabia at 3 p.m. on July 8, 2003. The dry bulb temperature stood at 108° at the time, so theoretically the heat index was 176°. Sharjah in the United Arab Emirates (UAE) apparently once recorded a dew point of 93.2° (date unknown) according to ‘Weather Climate Extremes’ Army Corps of Engineers TEC-0099 report.KUDOS: Thomas Schlatter of NOAA for USA dew point records and Dr. Adnan Akyuz, North Dakota State Climatologist for Moorhead, MN information.The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.