May 9: ORD

Today is May 9th. It's the 130th day of the year. 236 days remain. It's week 19 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 68 and the normal low is 46. I've calculated the 33-year averages at 71 and 48.

On the warm side, in 1979 (O'Hare's warmest May 9th) the high was a near-record 89 degrees with a low of 69. Both the high of 89 and low of 69 are O'Hare's warmest for May 9th. In 1993 the high was 87 with a low of 60. In 1987 the high was 85 with a low of 55, a 30 degree spread. In 2004 the high was 88 with a low of 52, a 36 degree spread. A year later, in 2005, the high was 77 with a low of 62. Two years prior, in 2003, the high was 84 with a low of 54, a 30 degree spread. In 2007 the high was 77 with a low of 61. The other warm highs were 81 in 1985 and 80 in 2001. The record high of 94 and record warmest low of 69 were set on the same hot day back in 1934 at the University of Chicago. Although O'Hare had a low of 69 in 1979, at the time it was not the official station of record for Chicago. Midway had a low of 67 in 1979. Furthermore, O'Hare's low was also 67 in 1965. 28 of the past 33 highs (85%) were in the: 60s (8), 70s (13) and 80s (7). Our most recent 80s high was 88 in 2004. The second warmest May 9th occurred in 1965 (high of 82, low of 67). O'Hare also had a warm high of 86 in 1963. On the cool side, five highs were in the 50s.

In looking back through the years to the first May at O'Hare in 1959, the following instances were notable: In 1977 the high was 51 with a low of 32, a cold day. In 1974 the high was a cold 49 with a low of 37, a cold day. In 1970 the high was 78 with a warm low of 61, a warm day. In 1966 the high was 44 with a low of 27, a cold day. 1966 was also the year of the record coldest high (42 at Midway). In 1965 the high was 82 with a low of 67, a warm day. In 1963 the high was a hot 86 with a low of 55, a 31 degree spread and warm day. In 1962 the high was a cool 52 degrees. In 1960 the high was a cold 41 with a low of 36, a five degree spread. That high of 41 was actually colder than the record coldest high, but keep in mind, O'Hare was not the official station of record for Chicago in 1960. In 1959 the high was 68 with a low of 46, temperatures which are the same as the normal high and low for May 9th.

More recently, we had additional large spreads of 34 degrees in 1981 (72/38) and 30 degrees in 1982 (76/46).

On the cool side, in 1983 the high was 55 with the record low of 27. Two years ago, in 2010, the high was 58 with a low of 38. The record coldest high of 42 was set in 1966. 24 of the last 33 lows (73%) were in the: 40s (13) and 50s (11). O'Hare recorded consecutive 40s & 50s lows as follows: eight from 1985 through 1992 and 11 from 1994 through 2004. Five lows (15%) were in the cold: 20s (1) and 30s (4). Four lows (12%) were in the warm 60s. O'Hare's coldest May 9th was in 1966 (high of 44, low of 27 (tied with 1983 as the coldest low of the date)). O'Hare's second coldest May 9th was in 1960 (the coldest high of the date of 41 with a low of 36).

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:07 and sunrise is at 5:38. Sunset is at 20:02 and twilight ends at 20:34. There's a total of 14 hours, 24 minutes of daylight today and 15 hours, 27 minutes between twilights. We gained two minutes of daylight from yesterday. Tomorrow twilight begins at 5:05 and sunrise is at 5:37. The moon is waning gibbous. Illumination was 86% at midnight, will be 82% at noon and 77% at midnight tonight. Moonset was at 8:53 this morning. Moonrise is at 0:02 tomorrow morning. Moonset is at 10:02 tomorrow morning. Moonlight time is 8 hours, 53 minutes which is 19 minutes longer than yesterday.