|Top 20 Coldest/Warmest Junes in Southeast Lower Michigan |
|Rank||Detroit Area*||Flint Bishop**||Saginaw Area***|
|* Detroit Area temperature records date back to January 1874.|
** Flint Bishop temperature records date back to January 1921.
*** Saginaw Area temperature records date back to January 1900.
Why the discrepancy between Detroit, Flint and Saginaw? Again, mainly because of the heat island effect at Detroit Metro Airport. And, not just the overnight lows on the hottest of days but also on the coolest of nights! The reason both Flint and Saginaw placed so much lower in the top 20 hottest Junes (or not at all) was the decidedly, refreshing cool blasts that occasionally occurred during the month. This was due to our friendly cool upper low pressure centered over eastern Canada that plopped its caboose far enough south over the Great Lakes and Northeast, to break the hot spells. Of course, these cooler infiltrations happened at Detroit too but on several occasions; that cooler air was introduced across the region on a north to northeast wind. This is not conducive to the coolest of nights at Metro with the wind flow across the urban and suburban areas into Metro Airport.
With all the heat lately, it is easy to forget the strong cool blasts Southeast Lower Michigan did see in June. As a comparison; Flint's temperatures fell into the 40s for overnight lows ten times during the month and two of those were 42 degrees, ten degrees from freezing! Saginaw saw overnight lows fall into the 40s five times with the lowest; a double 46. Detroit had a lone 49 degree low for the month but still, there were numerous 50s. Take away the heat island effect; and I doubt Detroit would have placed much above the mid teens in the top 20 warmest Junes, like Saginaw. Unfortunately, this micro-climate does affect temperatures (mainly overnight lows) at Detroit and several other major cities...polluting long term records (but don't get me started ;-)).
Last year's hot Summer of 2011; tied with 2010 in Detroit at 74.4 for fourth hottest summer! We also did end up with 23 days where the temperature rose to 90 degrees or better. Thus far we are moving right along on the 90 degree track again with already 11 days of 90 degrees or better at Detroit; average is about 12-14. Even though Flint did not place in the top 20 warmest Junes; there still were 7 days with 90 degrees or better in June and one 100 (8 for the season). This is the best example of the contrasting temperatures during the month! Here Flint has had 7 days of 90 degree or better, including the 100...yet failed to even place in the top 20 warmest Junes! Want more proof? Get a load of Flint's June temperature extremes...100 degrees and two 42 degrees!
Why so hot; yet "so cool" with average temperatures just 2 1/2 degrees above normal? DRY! That's right, the upper wind pattern thus far this summer has been conducive to bring the blistering heat out of the Great Plains and Midwest, east into the Great Lakes. While to a lesser extent, the upper flow over Canada has occasional been impressive enough to break through the hot ridge and back it off further west and thus keeping the worst of the heat; west and southwest of us until really just this past several days. While this has helped in the temperature department somewhat; it had added to the dry conditions. When these cooler air masses have surged out of Canada, they flow across the relatively, cool and dry continental regions of Canada. This, combined with the prevalence of the strong hot ridge west and over us; has lead to a relatively scant moisture supply being the usual Gulf summer moisture has been cut back some.
Since the hot ridge has been so dominant over the country; increasingly dry soil conditions are exacerbating the heat and thus, exacerbate the dry conditions. Simply put; they feed on one another! That's why it's been so easy to pop into the 90s...just look at your yard...it's becoming semi-arid out there in many places! This comes, of course, at the worse time possible in the growing season. Many areas are at least two to nearly four inches below normal in this years growing season! A season that still has at least two solid months left yet. I feel this dry weather phenomena is just as important as any heat (and there at least so far, we've had some relief).
Check out the latest Drought and Dry Index Map>>>
This map below, shows the growing season (90 day) precipitation (or really lack of), percent of normal departure.
And this map below, shows the expansion for the below normal rainfall for June (30 day percent of normal).
Note the worsening dry conditions as relayed by the percent of normal rainfall (or really, lack of).
With the dominance of the hot ridge of high pressure thus far, I will be updating my Summer Outlook for the region by boosting temperature departures a bit higher anyways than I originally indicated. On the precipitation side of things; drier conditions looked like they'd be most likely from I-69 south; across two-thirds of the region. Preliminary indications here are; I will likely encompass the whole region but want to look at some indicators.
So then; will strong hot upper ridge continue to be the dominant player in our weather or will it begin to be squashed more often by the Canadian Low? And what of severe weather? Thus far, most of the action has been around us, especially south...will this continue?
Look for my mid-summer update within a week or two!
Making weather fun while we all learn,
Bill Deedler -SEMI_WeatherHistorian