After a relatively mild summer across the American Midwest, excessive heat has settled in over the past two weeks. And, like an unwelcome houseguest, the late summer heat seems reluctant to leave.
High pressure, currently centered over Missouri, is responsible for the unseasonable temperatures, deflecting Pacific storm systems to the north and allowing intense sunshine to bake the region; afternoon highs have been in the mid to upper 90s (F), more than 15 degrees above average. While precipitation was excessive in late spring and early summer, drought has returned to the Heartland and both crops and woodlands are wilting in the oven-like heat.
Fortunately, a pair of cold fronts are poised to drop southeastward from the Canadian prairies and cooler temperatures are expected by the end of the week. Until then, we are reminded that the astronomical summer has not yet run its course and the season seems intent on dominating the region until the fall equinox (if not beyond). On the positive side, the dry, sunny weather may intensify the autumn colors in October, that glorious month which always rewards our patience; in addition, for those in the Mountain West, the persistent high pressure dome over the central U.S. has prolonged the monsoon moisture flow from the Gulf of Mexico and Sea of Cortez.
