...The Summer That Wasn't...
By: William R. Deedler, Weather Historian., WFO Detroit/Pontiac Mi
Temperatures during the late Spring of 1992 by all accounts were quite normal
across Southeast Lower Michigan. May was generally a pleasant but dry month
with temperatures averaging near normal. However, a subtle but definite change
was beginning to evolve in the weather pattern late in the month.
After a warm spell occurred mid-May with high temperatures climbing into the
mid 80s, a strong cold front raced southeast across the region on the 23rd, bringing
with it thunderstorms and much colder weather. The high on the 23rd reached 80
degrees in Detroit and 74 at Flint, but on the 24th, the best the mercury could do was
a cool 52 in Detroit and only 49 at Flint. Though the 52 at Detroit was not a record
low maximum (that chilly honor belongs to a "high" reading of only 44 in 1925), the
49 degree reading at Flint was, and both were more than 20 degrees below the normal.
Both cities did, however, establish record lows the following morning when the
temperature skidded down to 35 at Detroit and 30 at Flint. The rest of May remained
below normal which brought the monthly averages back to near normal. This turn to
sharply colder weather late in the month reflected a temporary shift in the Jet Stream.
A strong northwesterly wind blew from the Arctic southward into the Great Lakes
region. When looking back, this temporary shift in the upper wind pattern was a
foreboding of things to come during the Summer of 92.
Like its predecessor, the first half of the month of June was similar to the first half of
May with a rather dry and benign weather pattern. Temperatures averaged slightly
above normal with only minor deviations. Ironically, an abrupt change to much colder
weather was heralded in around the official start of summer (11:14 pm on June 20th),
between the 19th and 21st. In retrospect, this chilly annunciation of summer was
uncanningly accurate and most fitting for what became the second coldest summer
ever recorded in Detroit and the coldest at Flint since records began.
Just before the arrival of the unseasonably cold airmass, temperatures climbed to
what would be one of two 90s in Detroit and the only 90 in Flint that year. An
unusually strong and vigorous cold front was pushed across Southeast Lower
Michigan by a massive, cool high pressure system in southern Canada. The
temperature change between the 17th and 20th was quite impressive over the region.
Detroit and Flint both rose into the lower 90s (Detroit-92, Flint-93 ) on the 17th
but on the 20th, the day after frontal passage, readings barely climbed above the
50 degree mark (Detroit-52, Flint-51), a forty degree drop! Both of these readings
were record low maximums for the date. Low temperatures the next few mornings
were in the upper 30s to mid 40s with Detroit establishing a record low of 42 on the
21st and Flint missing its record low by two degrees with a low of 39 on the 22nd.
These are normal low temperatures in Southeast Lower Michigan for late April.
June averaged 2.2 degrees below normal at Detroit with a mean temperature of 65.5,
while Flint was 1.7 below normal with a mean temperature of 64.2. Had it not been
for the above normal temperatures the first half of the month, the monthly temperature
departures would have been greater. Like May, June was again on the dry side across
Southeast Lower Michigan with about two-thirds the normal rainfall.
The timing of the lousiest weather during the summer could have not been worse,
coming right at the time when the summer is usually at its best, July into August.
These months are usually heavy tourist and vacation months in the Great Lakes.
The month of July was just about a total wash-out, figuratively and literally. Not
only was the month abnormally cool, it was extremely wet, especially across the
northern suburbs of Detroit into Flint (where it ended up with the honor of being
the wettest July ever with 9.35 inches of rain, a hefty 6.54 above the normal).
Across the northern suburbs of Detroit, over 7 inches (7.32) fell in Farmington and
nearly 7 inches (6.92) was recorded in West Bloomfield. Officially at Detroit
Metropolitan Airport, 5.91 was tallied up during the month which was 2.81 above
normal. To add insult to injury, when it did rain, many times it was on or near the
weekend. Every weekend showed rain falling either on one or both of the days and
sometimes it wasn't just a passing shower. Flint measured nearly three inches of
rain (2.72) on Saturday the 18th. Then, later in the month at the start of the
weekend on Friday, the 31st, another 2.18 inches was dumped on the area. In
Detroit, during the 4th of July weekend, a half an inch of rain fell on Saturday.
Then on the following Saturday and Sunday (11th-12th), 1.24 inches accumulated,
not to mention the 1.04 that fell on Monday, the 13th. In fact, if your vacation fell
during that week of the 11th through the 19th, it rained every day but the last with
the rain totaling 3.75 inches. It was even worse in Flint, where rainfall measured a
whopping 4.70 inches for that vacation week!
July 1992 ended up the second coldest July on record at Detroit since 1870 with a
mean temperature of 68.8 (the coldest occurred in 1891 with 67.2). It was the coldest
July ever in Flint back to 1942 with a mean temperature of 66.9 (see Chart-1). Also,
while it was the 11th wettest July at Detroit, it made the top of the list at Flint with
the 9.35 inches that fell. When combining the cool temperatures and heavy rainfall,
all of Southeast Lower Michigan experienced the worst weather in July on record.
The other 10 wetter Julys in Detroit were not as cool, nor was the coolest July in
1891 a wet one. Interestingly enough, there were no record lows set in either Detroit
or Flint. One explanation would be with all the rainfall, cloud cover averaged above
normal (over 7 out of 10 tenths coverage for the month) and thus, this would somewhat
hold up the overnight low temperatures. While on the subject of cloud cover, sunshine
at Detroit averaged at pitiful 49 percent, down significantly from the 68 percent
normally enjoyed in July. As would be expected, there were record low maximum
temperatures set, two in both Detroit and Flint (see Chart-1). There were no 90 degree
temperature days in Southeast Lower Michigan during July, the month that usually has
the most with an average of 5.
It remained unseasonably cool right through August across Southeast Lower Michigan,
though it did begin to dry up somewhat with normal to below normal rainfall. An
average temperature of 66.7, which was 3.8 below normal, made it the 3rd coldest
August on record in Detroit. In Flint, the temperature averaged 65.2 degrees which
was 3.3 degrees below normal, making it the second coldest August on record. The
temperature did manage to top 90 (91) only for the second and last time in Detroit
that summer on August 10th, while Flint flirted with, but just missed its second 90
(89) the same day. Both cities only had six days during the month that averaged above
normal reflecting a series of cold fronts that routinely pushed through the area. Two
more record low maximums were established in Detroit, while one was set at Flint
(see Chart-1) but again, no record lows were managed.
The cooler than normal weather held into early fall with both Detroit and Flint
averaging a degree or two below normal in September. Precipitation again rose to
above normal levels with Detroit reporting the 7th wettest September on record with
5.55 inches or rain.
While there were a few theories floating around as to the cause of our unusually cool
summer, the most accepted and credited was the eruption of Mt. Pinatubo which
occurred exactly one year earlier (June 14-15th, 1991) in the Philippines. The volcanic
ash that was spewed into the atmosphere, circumnavigated the globe and caused a
slight decrease in solar warming into the following year.
The average temperature for the three month (June-August 1992) summer period
in Detroit was 67.0 which was 3.1 below the normal of 70.1 degrees. This made the
Summer of 1992 the second coldest on record back to 1870. The coldest was just
a half degree colder at 66.5 and occurred way back in 1915. The difference between
that summer and the Summer of 92 was June of 1915 was cooler (ave: 63.1) than
June of 1992, while July was warmer (ave: 70.4) and August again cooler (ave: 66.0).
In Flint, the temperature averaged 65.4 degrees which made it the coldest summer
on record back to 1942. Normally the summer temperature averages 68.4 through the
three month period (see Chart-1).
C H A R T - 1
Summer of 1992
______________________________________________________________________________________
T E M P E R A T U R E S --- PRECIPITATION
Monthly Average/Depart - Record Low Maximum/ - Record Low/ - Rainfall/
Dates Dates Depart
______________________________________________________________________________________
-MAY
DETROIT 58.3 + .2 ----- 35/25th 1.33/ -1.44
FLINT 57.3 + .9 49/24th 30/25th 1.64/ -1.14
--------------------------------------------------------------------------------------
-JUNE
DETROIT 65.5 - 2.2 52/20th 42/21st 2.35/ -1.08
FLINT 64.2 - 1.7 51/20th 46/28th 2.26/ - .97
--------------------------------------------------------------------------------------
-JULY
DETROIT 68.8 - 3.1 65/23rd, 65/30th ----- 5.91/ +2.81
FLINT 66.9 - 3.2 64/23rd, 64/30th ----- 9.35/ +6.54
--------------------------------------------------------------------------------------
-AUGUST
DETROIT 66.7 - 3.8 65/14th, 62/28th ----- 2.50/ +.71
FLINT 65.2 - 3.3 59/28th ----- 3.50/ +.12
--------------------------------------------------------------------------------------
-SEPTEMBER
DETROIT 61.4 - 1.9 ----- 5.55/ +3.30
FLINT 60.2 - 1.0 ----- * 34/23rd 2.50/ + .15
--------------------------------------------------------------------------------------
-SUMMER OF 92 (June - August)
DETROIT 67.0 - 3.1
FLINT 65.4 - 3.0
______________________________________________________________________________________
* superceded in 1995 with 27 degrees
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