The cooler than normal July temperatures which have slashed air conditioner bills across much of the Midwest and East Coast appear all but certain to establish a new temperature benchmark by the time the month ends at midnight Friday. With the reading of 86 degrees set back on the 6th likely to stand as the month's warmest since July 1, the month is likely to become the first July in 139 years of official records here which fails to produce a temperature of 87 degrees or warmer. Monday's 84-degree high -- far from an exceptionally warm reading -- was the city's warmest in 12 days.
Several clusters of thunderstorms are likely to sweep the Chicago area Tuesday. Half inch diameter hail accompanied storms in Ogle County Monday evening just northwest of Polo.
Severe storms produce tornado touchdown south of La Crosse, Wis.
Thunderstorms have erupted five of the past seven days somewhere in the mid and upper Midwest. Monday's storms produced a tornado touchdown 37 miles south/southeast of La Crosse, Wis., around 5:18 p.m. Law enforcement officials indicated the twister generated numerous reports of damage there. Storm downpours across southwest Wisconsin -- from the towering 50,000-foot-tall thunderheads responsible for that twister -- were impressive and included 1.62" at Friendship, 1.58" at Muscoda, 1.50" at Mineral Point and 1.46" at Fennimore.
Several clusters of thunderstorms are likely to sweep the Chicago area Tuesday. Half inch diameter hail accompanied storms in Ogle County Monday evening just northwest of Polo.
Severe storms produce tornado touchdown south of La Crosse, Wis.
Thunderstorms have erupted five of the past seven days somewhere in the mid and upper Midwest. Monday's storms produced a tornado touchdown 37 miles south/southeast of La Crosse, Wis., around 5:18 p.m. Law enforcement officials indicated the twister generated numerous reports of damage there. Storm downpours across southwest Wisconsin -- from the towering 50,000-foot-tall thunderheads responsible for that twister -- were impressive and included 1.62" at Friendship, 1.58" at Muscoda, 1.50" at Mineral Point and 1.46" at Fennimore.
When you report on temperature records for Chicago like this one (July headed for a ..close...not to reach 87 degrees), what temperature are you comparing it to and is that data raw data or has it been massaged?
My understanding is that it is from a weather station near/in O'hare (at least, since the 1940's or so).
Is the temperature data stored in the archive completely raw?
Has it been massaged in any way?
Does it take into account the urban heat island effect (i.e. does it have a negative correction to compensate?)
thanks,
Steve Trail, Ph.D. (chemistry, not weather related)
Steve, thanks for your comment. When we discuss official Chicago temperature records, we use the full historical data base that dates back to the early 1870s. That data base is "raw" and unaltered -- there is no bias or error correction to compensate for any weather effect (such as urban heat island or lakeshore cooling). The official Chicago site has moved around over the years, and has been at O'Hare since the early 1980s.
Official temperature readings are very accurate, as the instruments used offer a great deal of precision, are regularly checked and calibrated, and are ideally situated to eliminate recording errors (i.e. direct sunlight or proximity to man-made heating or cooling).
For our weather page, sometimes we will focus on strictly Midway Airport data since it offers the most full and continuous weather data set available for Chicago (1928 to present); in addition, it represents a more urban location than O'Hare. However, since that data set overlaps but does not match the official records, such analyses shouldn't be mistaken for those that use "official" Chicago data.
Anyway, hope that helps.
Tom,
Ninety degrees days do not make summer, "summer."
Sunshine does.
When was the last, "cloud free (not cloud gate!)" day in Chicago?
And I don't mean just for a few hours.
I mean from the time we wake up, to the time we go to sleep, there being no clouds. (Other than perhaps a white puffy one or two.)
The last day I remember that was cloud free was December 31st 2008. Granted it was cold that day (before the NHL Winter Classic), but at least it was "cloud free."
So again, when was the last "cloud free" day here in our lovely city?
I know we haven't had two "beach" (cloud free) days in a row. Right?!
Certainly not this year!!
WE LOOK FORWARD TO YOUR REPLY.
Sincerely,
Gary
Does anyone record temperature from the same location that we record temperature in the late 1800's? As I understand it, these temperatures are from the lake front and, the earliest mean temperatures are also the coldest: http://www.crh.noaa.gov/lot/?n=chi_jul_temp_rankings
Someone must have measured the temperature last month on the lake front to have an apples to apples comparison to 1891?
Short answer: No.
Longer answer: It's possible to do a comparison between the lakefront temps of 2009 vs. those of the late 1800s. The difficulty is that it won't be a true "apples to apples" comparison either because the readings recorded in the late 1800s were at various sites downtown -- and none of those sites come close to matching the location of today's lakefront temp sensor (near Northerly Island).
Chicago's most complete continuous temperature data base is at Midway Airport with records dating back to 1928.