October 9: ORD

Today is October 9th. It's the 283rd day of the year. 83 days remain. It's week 41 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 65 and the normal low is 45. I've calculated the 33-year averages at 64 and 45.

On the warm side, two years ago, in 2010 (O'Hare's second warmest October 9th), the high was the record-tying high of 86 (tied 86 in 1949 at Midway) with a low of 55, a 31 degree spread. Some other highs two years ago: Rockford: 90 (new record), West Chicago: 88, Midway: 87 (broke their own record), NWS/Romeoville: 88, Aurora: 89, DeKalb: 86, Joliet: 90, Northerly Island: 78. Last year, in 2011, the high was 80 with a low of 52. Last year's high of 80 is just the 5th 80s high in O'Hare's history for the date. The record warmest low of 68 degrees occurred way back in 1879, a time when the official readings were taken adjacent to Lake Michigan. 29 of the past 33 highs (88%) were in the: 50s (10), 60s (11) and 70s (8). Two highs were in the warm 80s (the past two years). Two highs were in the cool 40s (48 degrees in 1990 and again in 1993). O'Hare's warmest October 9th was in 1973 as the high was 81 with a low of 63 (O'Hare's warmest low of the date). O'Hare's second hottest high of the date is 83 degrees in 1966. O'Hare's other warm highs of the date are 80 degrees in 1961, 79 degrees in 1963 and 79 degrees in 1969. O'Hare's other warm lows are its second warmest of the date of 57 degrees in 1982 and 1984.

In looking back through the years to the first October at O'Hare in 1959, the following instances were notable: in 1978 the high was 73 with a low of 41, a 32 degree spread. In 1973 the high was 81 with a low of 63, a warm day. In 1969 the high was a warm 79 with a low of 40, a 39 degree spread. In 1967 the high was a cool 48 with a low of 37, a cool day. In 1966 the high was a warm 83 with a low of 49, a 34 degree spread. In 1965 the high was 57 with a low of 50, a seven degree spread. In 1964 the high was 44 (year of the record coolest high of 43) with a low of 24 (colder than the record low of 30), a cold day. In 1963 the high was a warm 79 with a low of 41, a 38 degree spread. In 1961 the high was a warm 80 with a low of 56, a warm day.

More recently, there was an additional large spread of 30 degrees in 1981 (62/32). There were small spreads of three degrees in 1990 (48/45), six degrees in 1983 (56/50) and six degrees in 1984 (63/57).

On the cool side, in 1993 (O'Hare's second coolest October 9th) the high was 48 with a low of 32. In 2000 the high was 57 with the record low of 30. The other cold lows are 32 degrees in both 1981 and 1989. Those 32 degree lows were all former record lows. The other cool highs are 48 degrees in 1967, 48 degrees in 1990, 52 degrees three years ago in 2009 and 53 degrees in 1986.  The record coolest high of 43 degrees occurred in 1964 at Midway. 16 of the last 33 lows (49%) were in the 40s. Eight lows (24%) were in the cold 30s. Nine lows (27%) were in the warm 50s. O'Hare's coolest October 9th was in 1964 as the high was 44 (O'Hare's coolest high of the date) with a low of 24 (O'Hare's coldest low of the date, a low that is colder than the record low).

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:32 and sunrise is at 7:00. Sunset is at 18:20 and twilight ends at 18:48. There's a total of 11 hours, 20 minutes of daylight today and 12 hours, 16 minutes between twilights. We lost three minutes of daylight from yesterday. Tomorrow twilight begins at 6:33 and sunrise is at 7:01. The moon is waning crescent, having passed last quarter yesterday at 2:33. Illumination was 41% at midnight, will be 36% at noon and 31% at midnight tonight. Moonrise was at 0:30 this morning. Moonset is at 14:53 this afternoon. Moonrise is at 1:32 tomorrow morning. Moonlight time is 14 hours, 23 minutes which is five minutes longer than yesterday. Moonlight time is at its peak today.  

Warm Fall began September 22nd and runs for 41 days through November 1st. High temperatures in this period are usually in the 50s, 60s and 70s. Highs in the 30s and 40s occur infrequently. United Nations Day is in 15 days. Standard Time doesn't return until November 4th.