One reporting station in western Canada reported a high of 92! On his blog, Jim Steenburgh, professor of meteorology at University of Utah, noted how unusual some of these temperatures were compared to average (or “climatology”):
Climatologically, the average maximum temperature is 66ºF in Seattle … compared with 93.7ºF in Phoenix and 90.5ºF in Tucson.
As summer-like as it was in the four corners of the U.S. (and areas of southeast and southwest Canada), it was cool and raw in many places in between. Atlanta, for example, only had a high of 59 Monday (D.C.’s high was 65).
A huge gap between the northern and southern branches of the jet stream drove the continental temperature contrasts. Because of the separation of the streams (marked by the arrows in Canada above), enough latitude existed for the development of large areas of high pressure near the U.S.-Canadian border. Under these big highs, the air compressed and warmed.
Meanwhile, above the southern jet stream zipping along the U.S. -Mexico border, areas of low pressure formed in the dips, generating cool, unsettled weather.
Characteristically at this time of year, these two streams of flow are closer together and the northern branch of the jet stream is farther south, preventing the development of warm air masses in Canada.
The gaping hole between the jet streams will disappear this weekend, as a big dip in the northern jet stream plunges south from Canada and comes together with the southern jet. A cold front will sweep across eastern North America along the leading edge of the diving jet stream, sweeping away the hot air in northern New England.
But as for now, it’s 83 degrees in northern Maine, 61 degrees in Washington, D.C. and 81 degrees in Miami. Crazy, no?