July 30, 1999 was a scorcher across the U.P. The official high at the National Weather Service (NWS) near Negaunee reached 97, tied with the record high for the date set in 1975. An upper-level ridge of high pressure bubbled into the Upper Great Lakes from the south, which helped to pump up the heat and humidity (Image above). Dew points reached into the 70s for much of the afternoon, making the hot weather most unpleasant.
Relief came quickly on this hot Friday; a cold front sweeping in from the west set off a line of violent thunderstorms that swept eastward affecting much of the Peninsula. The lightning display given off by the squall line was spectacular. Wind gusts toppled trees and caused power outages in the western U.P. before weakening slightly as the storms moved east.
This record high was the culmination of a warm summer month. In July 2014, it??s only reached 80 or above four times. In 1999, it happened 17 times at the NWS, including 12 consecutive days to end the month. From July 20-31, the mean temperature was 7.7 degrees above average. In contrast through the 29th, July 2014 is running 3.3 degrees below average.