August 22: ORD

Today is August 22nd. It's the 235th day of the year. 131 days remain. It's week 34 of the year.
 
Unless noted, the following data is based upon observations collected by the National Weather Service, Chicago, at O'Hare International Airport (ORD) between November 1978 and last year. ORD has been the official site of record for Chicago since Thursday, January 17, 1980. Before this, the official site of record was on the south side of Chicago at Midway International Airport (MDW), beginning on Wednesday, July 1, 1942. From Friday, January 1, 1926 through Tuesday, June 30, 1942, the official site was at the University of Chicago. Before that, the official site was at various locations in Chicago going back to Monday, October 16, 1871. Observations taken from October 15, 1870 to October 8, 1871 were lost in the Great Chicago Fire.

According to the National Climatic Data Center (NCDC), the normal high is 82 and the normal low is 63. I've calculated the 33-year averages at 82 and 62.

On the hot side, in 1996 the high was 89 with a low of 70. In 2007 the high was 90 with a low of 69. That high of 90 was the first 90s high since 1976 when it also reached 90 degrees. Although 1996 and 2007 are our warmest days since 1979, they are way short of the warmest of the date in O'Hare's history. The record high of 99 was set in 1936 at the University of Chicago. The record warmest low of 76 occurred in 1968 at Midway. 23 of the past 33 highs (70%) were in the 80s. One high (3%) was in the hot 90s. Nine highs (27%) were in the cool: 60s (1) and 70s (8). Our most recent 70s high was 73 degrees in 2005. O'Hare's warmest August 22nd was in 1968 as the high was 94 (O'Hare's co-hottest high of the date) with a low of 76 (O'Hare's warmest low of the date). O'Hare's second warmest 8/22 was in 1959 as the high was 94 (the other co-hottest high of the date) with a low of 74 (O'Hare's second warmest low of the date). The co-second hottest highs of the date are 93 degrees in 1962 and 1971. The back-to-back years of 1971 (93/68) and 1972 (90/72) were very warm as these days have means of 80.5 and 81 degrees respectively.   

In looking back through the years to the first August at O'Hare in 1959, the following instances were notable: In 1968 the high was 94 with a low of 76, a hot day. 1968 was also the year of the record warmest low. In 1967 the high was a cool 64 with a low of 59, a mere five degree spread. In 1962 the high was a hot 93 with a low of 55, a 38 degree spread. In 1961 the low was a cold 49 degrees. In 1959 the high was a hot 94 with a low of 74, a hot day.

More recently, there was a small spread of five degrees in 1990 (72/67) and a large spread of 32 degrees in 1992 (83/51).

On the cool side, three years ago, in 2009 (O'Hare's second coolest August 22nd), the high was 68 (the only 60s high of the last 33 years and O'Hare's second coolest high of the date) with a low of 57. The previous 60s high of 64 degrees (O'Hare's coolest high of the date) occurred 45 years ago in 1967. These were the only 60s highs in O'Hare's history for 8/22. Five years earlier, in 2004, the high was 80 with the record low of 49 (tied as O'Hare's coldest low of the date along with a low of 49 degrees in 1961). The former record lows were both 51 degrees, occurring way back in 1890 and over a century later in 1992. The record coolest high of 60 degrees occurred way back in 1890, at a time when the official readings were taken adjacent to  Lake Michigan. So as you can see, 1890 was Chicago's coolest August 22nd.  20 of the last 33 lows (61%) were in the 60s. O'Hare recorded six consecutive 60s lows from 1978 through 1983. Ten lows (30%) were in the cool: 40s (1) and 50s (9). Three lows (9%) were in the warm 70s. O'Hare's coolest August 22nds have means of 61.5 degrees in: 1961 (high of 74, low of 49 (co-coldest low with 2004)) and 1967 (high of 64 (coolest high of 8/22), low of 59).    

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:39 and sunrise is at 6:09. Sunset is at 19:43 and twilight ends at 20:12. There's a total of 13 hours, 34 minutes of daylight today and 14 hours, 33 minutes between twilights. We lost two minutes of daylight from yesterday. Tomorrow twilight begins at 5:40 and sunrise is at 6:10. The moon is waxing crescent, heading towards first quarter in two days at 8:54. Illumination was 25% at midnight, will be 30% at noon and 35% at midnight tonight. Moonrise is at 11:55 this morning. Moonset is at 22:15 tonight. Moonrise is at 13:06 tomorrow afternoon. Moonlight time is 10 hours, 20 minutes which is 33 minutes shorter than yesterday.

Summer began on June 4th and runs for 110 days through September 21st. High temperatures in this period are usually in the 70s and 80s. Highs in the 90s and 100s occur infrequently. Labor Day is in 12 days.