UPDATED at noon to include more historical information.
It was a pleasant 71 degrees at 7 a.m. today. Remember it well.
A welcome but temporary puff of Canadian air is being shoved aside by the powerful high-pressure system that is building over the Plains and Midwest. The National Weather Service is forecasting a high of 99 today and 108 — yes, 108 — on Thursday, followed by temperatures above 100 through Monday.
No relief is in sight. By noon today, the temperature had risen to 88, the normal high for this time of year.
"What we're seeing right now is more typical of late July and August," said Scott Truett of the Weather Service office in Weldon Spring. "The worrisome thing is that we're already dry, and we're heading into what normally is our driest time. None of this bodes well."
St. Louis city officials have issued a heat advisory in the city until 7 p.m. Saturday. The advisory urges people to check on family and neighbors who are vulnerable to the heat.
The Weather Service says the last time St. Louis recorded five consecutive days at or above 100 degrees was in July 1983. The last time St. Louis had a high temperature of 108 or more was on July 18, 1954, when the temperature was 112. Four days before that, the hottest ever on record here was posted -- 115 degrees on July 14, 1954.
So far, the hottest temperature ever recorded in St. Louis in June is 105 degrees, reached on June 19, 1936, and June 29, 1952.
In 1980, the last severe heat wave in St. Louis, the temperature reached 107 on July 15. That year recorded 18 days of highs of 100 or worse, and 153 deaths were blamed on the heat.
Record daily highs for late June and early July are all above 100. A hot spell in 1952 accounts for the records for today's date through Friday's, when the temperature reached 105.
Wes Browning of the local Weather Service office says the temperature could hit 108 tomorrow because the core of the high-pressure system is drifting eastward. Browning said it likely diminish by Friday, but provide only the relative "relief" of 104 degrees. He said the pattern otherwise will hang on.
Last summer, the first 100-degree day was on July 11. There were 15 days at or above 100 degrees last year, causing 19 heat-related deaths. The high last year was 104 on Sept. 3.
As for the dry part of the bad news, St. Louis hasn't had rain since June 16. Only 2 inches of rain have fallen this month, almost 2 inches below normal for June. And that was after a dry May, when rainfall was three inches below normal.
The Weather Service considers the St. Louis area abnormally dry and the surrounding areas in eastern Missouri and Southern Illinois in moderate drought. Extreme drought conditions exist in far southeastern Missouri and Southern Illinois.
Truett said the temperature exceeded 100 Tuesday in parts of eastern Kansas.
"Drought conditions over the Plains tend to expand and become a kind of self-fulfilling prophecy — hot and dry, hotter and more drought," he said.
Meanwhile, Edwardsville issued a voluntary water-conservation advisory effective today to maintain its water system. The city urges residents to avoid watering lawns or gardens during the day and to cut back on watering and washing vehicles.