With just a few more days to go, July 2011 is shaping up to be THE hottest month in recent memory across Southeast Lower Michigan and one of the hottest, if not THE hottest, on record (depending on location and records). As you can see by the table below, Detroit hottest month is shared by July from two different years: 79.0 degrees in both 1955 and 1921. Flint's hottest month on record comes in at 78.0 degrees, also back in 1921, while Saginaw is at 77.5 in again, 1921. So basically, the hot July of 1921 is the beast to beat at all three sites. Ironically, this is nearly a century ago and not in recent records (something to think about). It just adds credence to statement I've made several times in the past when the media or general public say, "this has never happened before" or "this is unprecedented"! Most of the time, I just answer: "yes it has" (or something close to it). This, along with interest and fascination on my part, are the reasons I wrote so many articles on weather history and events in Southeast Michigan...to satisfy that curiosity. Back to 1921, the urban expansion and heat island at Detroit was much less than in 1955 or today. Still, was it enough to influence the temperatures since Detroit's climatological station was downtown in the City? Probably a bit, but a check of overnight lows and daily temperature ranges that month (compared to Flint and Saginaw) would clear the picture some. What is needed is a comparison of July's highs and lows for both 1921 (and let's not forget 1955) with this year (and I don't have the detailed data in front of me). An educated assumption on my part is that Detroit's climate back in 1955 had more of a urban influence than 1921 since as it was still downtown (at DET, Detroit City Airport) and there was quite the urban sprawl between 1921 and 1955. Even stronger evidence for some urban heat influence back in 1955 at Detroit is that both Flint and Saginaw placed lower that month in 4th and 5th place, respectively (see below) for hottest month. The most important fact is that July of 1921 comes up as the hottest month at all three sites, strong verification it was"THE" hottest of times in old Southeast Michigan. Another important fact (especially with public perception) is what type of heat engulfed the region in both 1955 and 1921? Were they hot and humid months or hot but somewhat "drier air months" (so to speak, meaning less humidity and similar to that of June of 1988). The dew points and subsequent humidities along with overnight lows in both months would tell the story. If one or both were a "drier air months", the residents of Southeast Michigan would at least get some relief from the heat, especially at night. In addition, did the drier trend prevail or was it only a few nights. In any event, when just comparing apples to apples (temperatures), July of 2011 is fast going to down in climate history books as the record or near record hot month. This will depend on what happens between now and the end of the month (which looks to be accommodating with more heat and above normal temperatures). Detroit as of 7/25/11 has an average temperature of 79.5 /79.0-1955 & 1921 record/ and thus, now sits in first place for hottest month! The average high temperature for July thus far is an incredible 89.6 /90/ degrees while the average low is sitting at 69.3 degrees. Flint is averaging an even 77.0 degrees /3rd-place, 78.0-1921 record/ for hottest month. Flint's average high is nearly as hot as Detroit with 89.2 but with a substantially cooler average low coming in at 64.8 degrees (4 1/2 degrees lower than Detroit). This could be the result of a number of factors: the lack of urban heat influence (it's still relatively rural around the site) along with cloud cover and rainfall. Detroit has been notably wetter than Flint up to this point with 3.23" falling at Detroit compared to Flint's meager .45" (and this would, at times, tend to inhibit overnight lows from falling as much at Detroit). Finally at Saginaw with an average temperature of 76.3 degrees /3rd-place, 77.5-1921/ and an average high of 86.6 and low of 66.0 (note, a bit higher than Flint) is also sitting at the 3rd hottest month, thus far. Stay Tuned. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Rank | Detroit Area* | Flint Bishop** | Saginaw Area*** | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Coldest | Warmest | Coldest | Warmest | Coldest | Warmest | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Temp | Year | Temp | Year | Temp | Year | Temp | Year | Temp | Year | Temp | Year | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| 1 | 12.2 | Feb-1875 | 79.0 | Jul-1955 | 10.9 | Jan-1977 | 78.0 | Jul-1921 | 9.4 | Jan-1912 | 77.5 | Jul-1921 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| 2 | 12.8 | Jan-1977 | 79.0 | Jul-1921 | 12.8 | Feb-1979 | 77.7 | Jul-1935 | 10.4 | Jan-1918 | 76.8 | Jul-1916 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| 3 | 13.1 | Jan-1912 | 77.9 | Jul-1916 | 13.1 | Jan-1963 | 76.7 | Jul-1934 | 11.6 | Jan-1963 | 76.2 | Jul-1935 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| 4 | 13.2 | Jan-1918 | 77.7 | Jul-1931 | 13.4 | Feb-1978 | 76.5 | Jul-1955 | 11.7 | Feb-1904 | 76.0 | Jul-1931 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| 5 | 14.8 | Feb-1934 | 77.1 | Aug-1995 | 13.8 | Jan-1994 | 76.1 | Jul-1931 | 12.1 | Jan-1994 | 75.9 | Jul-1955 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
7/26/11
July 2011 in the Running for One of the Hottest...If Not THE Hottest...Month in Detroit ! t!
7/25/11
Summer Dry Spells in Southeast Michigan
The latest dry spell affecting some in Southeast Michigan reminds me
of an article I wrote back in the late '90s. While working with the NWS, like anywhere else, I noticed numerous patterns and trends in our weather that would repeat over time. I researched and wrote about many weather events and trends. The following article (originally written in 1997) was about one such pattern.
of an article I wrote back in the late '90s. While working with the NWS, like anywhere else, I noticed numerous patterns and trends in our weather that would repeat over time. I researched and wrote about many weather events and trends. The following article (originally written in 1997) was about one such pattern.
...SUMMERTIME DRY SPELLS IN SOUTHEAST LOWER MICHIGAN ARE MORE COMMON
THAN YOU MIGHT THINK...
WRITTEN BY: WEATHER HISTORIAN BILL DEEDLER NWS WHITE LAKE MI
THE RECENT DRY SPELL THAT MOST OF THE AREA HAS SEEN THIS JULY IS
FAIRLY COMMON ACROSS SOUTHEAST LOWER MICHIGAN. IN FACT...IT IS RARE
NOT TO HAVE A NOTABLE DRY PERIOD DURING THE SUMMER MONTHS (JUN-AUG).
LOOKING BACK AT THE LAST 30 YEARS (1967-96) CLIMATIC STATISTICS IN
DETROIT SHOWED SOME INTERESTING AND SOMEWHAT SURPRISING DRY SPELL
TRENDS.
FIRST...THERE MUST BE SOME GENERAL DEFINITION OF A "DRY SPELL"
INCLUDING RAINFALL AND DURATION. HERE...CLIMATIC STATISTICS OF THE AREA
SHOULD BE THE GUIDE. THEREFORE...A DRY SPELL IN SUMMER DURING THE PAST
30 YEARS COULD BE DEFINED AS...LIGHT AMOUNTS OF RAIN (.50 OR LESS)
FALLING ON ONLY A FEW OF DAYS IN A PERIOD OF GENERALLY 2 TO 4 WEEKS.
THIS IS OPPOSED TO THE MORE SEVERE "DROUGHT" WHICH IS MORE PRONOUNCED
IN BOTH RAINFALL DEFICIENCY AND DURATION.
IN THE PAST 30 YEARS USING THIS DEFINITION...NEARLY 9 OUT OF 10 TIMES
(OR 87% OF THE TIME) SOUTHEAST LOWER MICHIGAN EXPERIENCED A NOTABLE
DRY SPELL SOMETIME DURING THE SUMMER MONTHS. THUS...IT IS UNUSUAL NOT
TO HAVE A DRY SPELL IN THE SUMMER. THE YEARS THAT SHOWED NO SIGNIFICANT
DRY PERIOD IN THE SUMMER WERE...1972...1977...1987 AND THE COOL SUMMER
OF 1992. IT IS INTERESTING TO NOTE...THESE "WET" SUMMERS WOULD HAVE COME
EXACTLY EVERY 5 YEARS SINCE 1972 IF THE AUGUST OF 1982 HAD NOT HAD A
PRONOUNCE DRY SPELL. SOME MONTHS DID END UP WITH SIGNIFICANTLY LESS
THAN NORMAL RAINFALL BUT DID NOT FALL IN THE DRY SPELL CATEGORY BECAUSE
THE RAINFALL WAS FAIRLY EVENLY DISTRIBUTED.
NEARLY TWO THIRDS OF THE TIME WHEN A DRY SPELL OCCURRED...IT WAS THE
ONLY DRY SPELL THAT SUMMER. THE OTHER THIRD OF THE TIME...WHEN THERE
WAS ONE DRY SPELL...ANOTHER FOLLOWED LATER IN THE SUMMER. ONE OF THE
MORE SURPRISING AND NOTABLE ITEMS TO COME OUT OF THIS BRIEF STUDY WAS
THE SHIFTING OF THE DRY SPELLS OVER THE YEARS. FROM THE MID 1960S
THROUGH THE 70S...IT WAS UNHEARD OF TO HAVE A NOTABLE DRY PERIOD IN
JUNE. AT THE SAME TIME...9 OUT OF THE 13 AUGUSTS (1967-79) HAD ONE OR
MORE DRY SPELLS WITH JULY ABOUT HALF AND HALF. YET IN THE 1980S AND
EARLY 90S...THE REVERSE TOOK PLACE. THE DRY SPELLS SHIFTED BACK INTO
EARLY TO MID SUMMER WITH ONLY TWO YEARS (1982/83) HAVING A DRY SPELL
IN AUGUST. SINCE 1994...DRY SPELLS IN AUGUST HAVE BEGUN TO REAPPEAR.
AUGUST 1996...FOR INSTANCE...WAS THE FOURTH DRIEST ON RECORD IN
DETROIT SINCE 1872 WITH ONLY .43 OF RAIN FALLING (NORMAL 3.43).
LOOKING AT EACH MONTH INDIVIDUALLY...THE DRY PERIODS IN JUNE HAVE
BEEN ALMOST EXCLUSIVELY MID TO LATE MONTH...WHILE IN JULY THEY
OCCURRED AT ALMOST ANYTIME AND IN AUGUST...THE PREFERENCE WAS AGAIN
MID TO LATE MONTH AND FREQUENTLY LASTED INTO SEPTEMBER. WHILE THESE
DRY SPELLS CAN OCCUR AT ANYTIME DURING THE SUMMER...THE CHANCES
GRADUALLY INCREASE AS THE SUMMER EVOLVES. THE BEST CHANCE FOR A DRY
SPELL HISTORICALLY IS FROM MID AUGUST INTO EARLY SEPTEMBER WITH MID
JULY TO EARLY AUGUST A CLOSE SECOND.
ONE OF THE MORE MEMORABLE EXTENDED DRY PERIODS IN RECENT TIMES
OCCURRED DURING THE HOT SUMMER OF 1988. DROUGHT OR NEAR DROUGHT
CONDITIONS DEVELOPED LATE IN THE SPRING AND CONTINUED UNTIL MID JULY.
FROM LATE MAY INTO THE THIRD WEEK OF JUNE ONLY .39 RAIN FELL IN
DETROIT. THEN ANOTHER VERY DRY PERIOD TOOK PLACE FROM LATE JUNE INTO
MID JULY WHEN ONLY .04 FELL. THIS DESERT-LIKE ATMOSPHERE...AS MOST
INHABITANTS OF THE AREA CAN ATTEST...WAS OFTEN ACCOMPANIED BY DESERT-
LIKE TEMPERATURES. MAY OF 1988 WAS THE THIRD DRIEST MAY (.87) ON RECORD
IN DETROIT...WHILE JUNE WAS THE SECOND DRIEST JUNE (.97). THIS ARID
CLIMATE CAME AT THE WORST TIME POSSIBLE...EARLY IN THE GROWING SEASON
...A TIME WHEN CONVECTIVE RAINS NORMALLY BEGIN.
OTHER DRY MONTHS NOTED WERE...JUNE 1984 (1.04)... JULY 1974 (.59)
...JULY 1984 (.95) AND AUGUST 1982 (.72). THE LEAST AMOUNT OF RAIN
EVER RECORDED IN DETROIT DURING A SUMMER MONTH WAS A MEAGER .16
IN AUGUST 1894. THE SECOND HIGHEST AMOUNT OF RAIN IN A SUMMER MONTH
ALSO OCCURRED IN AUGUST...AUGUST 1926 WITH 8.33 INCHES (JULY 1878
WAS THE HIGHEST WITH 8.76). CLEARLY...THE SUMMER MONTHS CAN BE
"FEAST OR FAMINE" WHEN IT COMES TO RAIN.
Dry/Drought map for SE Michigan as of 7/19/11. Note this is a broad scale average and
not fine tuned to a local areas.
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