September 8: ORD

Today is September 8th. It's the 252nd day of the year. 114 days remain. It's week 36 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 this, 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 78 and the normal low is 58. I've calculated the 33-year averages at 78 and 59.

On the hot side, in 1985 the high was 94 with a low of 67. Six years later, in 1991, the high was 88 with a low of 67. The other hot highs were 92 degrees in 2002 (our most recent) and 90 degrees in 1983. The record high of 96 degrees was last set in 1960 at Midway, after previously being set in 1959 (also at Midway) and originally in the city in 1933. Our most recent 70s low was 70 in 1964. The record warmest low of 76 occurred way back in 1922, a time when the official readings were taken adjacent to Lake Michigan. 27 of the past 33 highs (82%) were in the: 70s (14) and 80s (13). O'Hare recorded nine consecutive 70s & 80s highs from 1986 through 1994. Three highs were in the hot 90s. Three highs were in the cool 60s. O'Hare's warmest September 8th was in 1959 as the high was 97 (O'Hare's hottest high of the date) with a low of 71 (O'Hare's warmest low of the date). O'Hare's second warmest September 8ths were in: 1971 (high of 94, low of 69) and 1978 (high of 95 (O'Hare's second hottest high of the date), low of 68)). The two other hot days were in 1960 (high of 93, low of 69) and 1964 (high of 92, low of 70 (O'Hare's second warmest low of the date)).

In looking back through the years to the first September at O'Hare in 1959, the following instances were notable: in 1978 the high was a hot 95 with a low of 68, a hot day. In 1976 the high was a hot 90 with a low of 57, a 33 degree spread. In 1971 the high was a hot 94 with a low of 69, a hot day. In 1967 the high was 83 with a low of 50, a 33 degree spread. In 1966 the high was 81 with a cold low of 44, a 37 degree spread. In 1965 the high was 67 with a low of 61, a six degree spread. In 1964 the high was 92 with a low of 70, a hot day. In 1960 the high was a hot 93 with a low of 69, a hot day and year of the record high of 96 at Midway. In 1959 the high was 97 (hotter than the record high) with a low of 71, a hot day.

More recently, there were large spreads of 38 degrees in 1983 (90/52) and 32 degrees in 2002 (92/60). There were no small spreads of up to seven degrees.

On the cool side, in 1986 (O'Hare's coolest September 8th) the high was 73 with the record low of 43, a 30 degree spread. In 1979 (O'Hare's second coolest September 8th) the high was 66 with a low of 51. O'Hare's coolest high of the date is 65 degrees in 1995. The record coolest high of 54 occurred way back in 1883, a time when the official readings were taken adjacent to Lake Michigan. 31 of the last 33 lows (94%) were in the: 50s (14) and 60s (17). Two lows were in the cold 40s. There's an ongoing, 25-year streak of 50s & 60s lows that began in 1987 and ran through last year, 2011. O'Hare's second coldest low of 44 degrees occurred in 1966, part of a wild day which saw a high that was 37 degrees above that at 81 degrees.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:58 and sunrise is at 6:26. Sunset is at 19:14 and twilight ends at 19:43. There's a total of 12 hours, 48 minutes of daylight today and 13 hours, 45 minutes between twilights. We lost three minutes of daylight from yesterday. Tomorrow twilight begins at 5:59 and sunrise is at 6:28. The moon reaches last quarter today at 8:15. Illumination was 53% at midnight, will be 48% at noon and 43% at midnight tonight. Moonset is at 14:16 this afternoon. Moonrise is at 23:51 tonight. Moonset is at 15:03 tomorrow afternoon. Moonlight time is 14 hours, 25 minutes which is two minutes longer 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 60s, 90s and 100s occur infrequently. Grandparents Day is tomorrow. 9/11 Remembrance Day is in three days.