It's not unusual for a burst of cool weather to make an occasional summer appearance in the Midwest.
But according to the National Weather Service, it is unusual to get the intense, week-long burst of unseasonably cool weather the metro-east will experience this week. So much so that a temperature record that stood for 123 years fell Tuesday.
"This weather pattern is coming from an upper low pressure system that is allowing a surface high pressure system to rush in from Canada across the Great Lakes," National Weather Service meteorologist Jim Sieveking said. "While we see this from time to time, this has been more extreme than usual and set us up for a record low high temperature."
The high temperature Tuesday reached only 76, 13 degrees lower than the average high temperature for July 15 in the St. Louis area, according to the National Weather Service. The previous record for the lowest high temperature on this date came on July 15, 1891, with a high of 77.
"This is usually one of the hottest times of the year, so it seems very unusual to have this cool weather," Sieveking said. "But I haven't heard anyone complain about it -- except people who have pools or who operate pools who are upset that it's too cool to swim."
Chris Eckert, president of Belleville based Eckert's Orchards said the cool weather couldn't be better for his crops.
"I think the plants are loving it," Eckert said. "We've had a beautiful growing season. There has been just enough rain -- and right when we needed it. Nothing is burning off the trees and it's not too hot to work in it."
Eckert said the cool temperatures are especially good for young fruit trees. He said peach and apple trees are vulnerable until they're two or three years old.
"When you have a summer like we did in 2012 there's no energy for the plants to grown and produce new wood," Eckert said. "But when the weather is like this they grow chutes and branches very quickly. So this is great weather for us."
Eckert noted that the cool temperatures would slow the ripening of tomatoes but the crop will be fine.
While the high temperature was the lowest it's ever been, the overnight lows are nowhere near cold enough to worry about frost damage. The record for overall lowest temperature on July 15 is 52 degrees set in 1930. Metro-east residents fell short of that mark at 55 overnight.
The mercury will top out at 78 Wednesday under sunny skies. That would not break the record low high temperature of 73 set on July 16, 1958. The low temperature will be 58 overnight, five degrees higher than the record all-time low of 53 set on July 16, 1930.
On Thursday the high will be 76 under mostly sunny skies. That mark would tie the all-time lowest high temperature for July 17 set in 1938. The projected low of 58 would be one degree higher than the all-time low of 57 set in 1976.
Sieveking said the cool weather this week has nothing to do with the extremely cold winter or slow to warm up spring this year.
"It's just the weather pattern that has emerged right now," Sieveking said. "It could be completely different in a week."
Contact reporter Scott Wuerz at email@example.com or call 239-2626.