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  • Tim McGill

But, Oh, The Summer Nights

Chicago's Summers Getting Are Warmer

Meteorological summer started on June 1st. The season has started warm with temperatures running about 4.1° above average. Average highs for this time of the year are around 77°. Today should be the second straight day with a high in the 90s. Gusty southwest winds will send highs to 90° or above for most of us.

Gusty southwest winds will diminish just a bit tomorrow but it will remain breezy through Sunday afternoon. The humidity should remain tolerable today with dew points relatively low for highs in the 90s. Sunday will be slightly more steamy as dew points climb a few degrees. Dew points will eventually slide into the 60s by Sunday evening setting us up for a muggy Monday. There is a slight chance for an isolated shower or thunderstorm Sunday afternoon or evening but rain should be scarce this weekend.

The meteogram below considers several different model forecasts of temperatures. After our hot weekend we will see warm weather stick around through next week. Higher dew points mean it will be more muggy too. Highs will be around 7° to 13° above average Monday through Friday.

The heat has been turned up a notch for summers in Chicago. The average temperature (maximum plus minimum divided by two) has increased around 1° in the past fifty years.

The nights are warming disproportionately compared to the days. The average low temperature has jumped 1.6° over the past 50 years.

We certainly aren't alone. The vast majority of our county has warmed over the past fifty years with the exception of portions of a few plains states.

Climate Central did an analysis where they evaluated 51 years of summer temperature data in 246 U.S. locations.

Here are some of their conclusions:

  • Rising average temperatures: About 95% (233) of the locations had an increase in their average summer temperature, with 50% (122) of those increasing by 2° or more.

  • A fast-warming Western region and Texas: Nine out of the top ten fastest-warming summer locations were located in the Western U.S. and Texas, with Reno, Nev. (10.6°), Las Vegas (5.6°), and El Paso, TX (5.5°) in the lead.

  • Warmer summer nights: Summer night temperatures increased by 2° or more in 61% of the locations.

  • And more extremely hot days: 38% of locations reported, on average, at least one additional week of extremely hot temperatures annually (compared to 1970) and 59% have reported an annual increase of at least three days. The largest change is in Miami with 79 additional days above a sizzling 90°.

Heat is the #1 weather related killer. Cities like Chicago are getting a double whammy because of the "urban heat island" effect. Earth.org offers this explanation:

Deforestation and rapid urbanization cause changes in the natural landscape. In high-density cities like Hong Kong, green open space is gradually replaced by skyscrapers, traffics and infrastructure. Permeable vegetation became impermeable concrete. Scientists have discovered that when compared to rural environments, the modified land surface (such as dark pavement and roofing) in the urban areas affects the storage and transfer of both radiative and turbulent heat.

Drought Update

I updated the status of our drought yesterday. Here is a recap:

We are approaching the driest month of summer just as our drought deepens further. July on average sees 3.71" of rain making it the driest month of summer but June is starting off dry and the longer range outlooks for this month aren't particularly encouraging. I discuss this further below.

We have gone nearly eight weeks with less than two inches of rain. We just came out of the 3rd driest May on record. O'Hare is now down 7.49" of rain below average since March 1st, the start of spring.

The latest analysis from the U.S. Drought Monitor shows the area experiencing a severe drought has expanded by 62% compared to last week. Last week 2.85% of northern Illinois was in that category of drought and now it stands at 4.58%. Portions of DuPage & Cook counties, northern Kane county, all of Lake county and of McHenry county are now in a severe drought. There was a slight increase from 6.58% of the area experiencing a moderate drought last week to 6.92% this week.

The most parched portions of our area have seen between 25% to 50% of average rainfall over the past sixty days (ending on June 3rd).

Our neighbors to the north in Wisconsin saw a significant jump in the portion of their state experiencing a severe drought. Last week just .18% of the state was in a severe drought but now 5.09% has moved into that category. That's a 28 fold increase.

There is a slight chance for an isolated shower or thunderstorm Sunday afternoon or evening but most of this weekend will remain dry. A better chance for at least some scattered afternoon/evening showers and thunderstorms arrives by Monday and another round is possible later Tuesday into early Wednesday.

The GFS model total rainfall forecast through next Friday squeezes out about a half inch to an inch of rain. While any rain is welcomed at this point, we would pick up about an inch of rain in total for the next seven days on average. More rain than this is needed to put a real dent in our drought.

The long range precipitation probability forecasts are even more discouraging. The signal is strengthening for a drier than average middle of the month. The latest 6-10 day forecast has us outlooked for below average precipitation overall from June 10th through June 14th. The longer range 8-14 day forecast has even higher probabilities for a relatively dry period. It also has us favored for below average precipitation overall from June 12th through June 18th. This would mean both an expansion and deepening of our drought.

Here is my 7 day forecast:

Today: Sunny, hot & breezy High: 92

Sunday: Mostly sunny, hot, a bit breezy Low: 71 High: 91

Monday: Partly to mostly cloudy, isolated pm t-storm possible Low: 72 High: 89

Tuesday: Sun & cloud mix, sct. shower/t-storm possible Low: 70 High: 87 (cooler lakeside)

Wednesday: Sun & cloud mix, sct. shower/t-storm possible Low: 68 High: 85 (cooler lakeside)

Thursday: Sun & cloud mix, sct. shower/t-storm possible Low: 67 High: 85 (cooler lakeside)

Friday: Sun & cloud mix, sct. shower/t-storm possible Low: 66 High: 84 (cooler lakeside)



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