May 6: ORD

Today is May 6th. It's the 127th day of the year. 239 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 67 and the normal low is 45. I've calculated the 33-year averages at 69 and 46.

On the warm side, in 2000 (O'Hare's warmest May 6th) the high was 86 (O'Hare's warmest high of the date) with a low of 62. In 1986 (O'Hare's second warmest May 6th) the high was 84 with a low of 63. In 2004 the high was 83 with a low of 55. In 1982 the high was 82 with a low of 54. In 1998 the high was 77 with a low of 58. In 2002 the high was 75 with a low of 60. The other warm high was 81 in 2008. The record high of 91 was set in 1949 and the record warmest low of 66 occurred in 1965, both at Midway. 14 of the past 33 highs (43%) were in the 70s. On the warm side, five highs (15%) were in the 80s. The notable, pre-1979 warm high was 85 in 1959. 12 highs (36%) were in the cool: 50s (5) and 60s (7). Two highs (6%) were in the cold 40s (42 in 1989 and 48 in 1991).

In looking back through the years to the first May at O'Hare in 1959, the following instances were notable: in 1976 the high was a cold 43 with a low of 35, a cold day. In 1975 the high was a cold 52 degrees. In 1974 the high was a cold 51 with a low of 36, a cold day. In 1970 the high was a cold 51 with a low of 34, a cold day. In 1969 the high was 78 with a warm low of 63, a warm day. In 1968 the high was 61 with a cold low of 31, a 30 degree spread. In 1967 the high was a cold 53 with a low of 35, a cold day. In 1966 the high was 70 with a low of 40, a 30 degree spread. In 1965 the high was 77 with a warm low of 66, a warm day. 1965 was the year of the record warmest low, also 66 at Midway. In 1964 the high was 77 with a warm low of just 65, a warm day. In 1963 the high was 69 with a low of 38, a 31 degree spread. In 1959 the high was a warm 85 with a low of 53, a 32 degree spread and warm day.

More recently, we had a small spread of six degrees in 1991 (48/42). The large spreads were 36 degrees in 1987 (76/40), 35 degrees in 2008 (81/46), 33 degrees in 1993 (78/45), 33 degrees in 1995 (72/39), 32 degrees in 1980 (73/41), 32 degrees in 1988 (77/45) and 31 degrees in 1983 (77/46).

On the cold side, in 1989 (O'Hare's coldest May 6th) we had our record coldest high of 42 with a near-record low of 31. In 1981 the high was 50 with a low of 36. In 1992 the high was 59 with the record low of 30. The other cold or cool highs were: 48 in 1991, 53 in 1996 and 54 in 1994. 16 of the last 33 lows (49%) were in the 40s. Six lows (18%) were in the cold 30s. 11 lows (33%) were in the warm: 50s (8) and 60s (3). Our most recent 30s lows were 37 in 1994, 39 in 1995 and 39 in 1996. 1976 was O'Hare's second coldest May 6th with a high of 43 and low of 35. Another notable cold low was 31 degrees in 1968.

There was an instance of back-to-back years in which temperatures were just about as opposite as they can be. In 1981 the high was 50 with a low of 36, overall 13 degrees BELOW normal. Then in 1982 the high was 82 with a low of 54, overall 12 degrees ABOVE normal.

Today is a major day in Chicago's snow history. Twenty-three years ago (1989) we had half an inch of snow at O'Hare. Rockford had but a trace.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:11 and sunrise is at 5:42. Sunset is at 19:59 and twilight ends at 20:30. There's a total of 14 hours, 17 minutes of daylight today and 15 hours, 19 minutes between twilights. We gained two minutes of daylight from yesterday. Tomorrow twilight begins at 5:09 and sunrise is at 5:41. The moon is waning gibbous, having passed full last night at 22:35 as the full Flower moon (a.k.a. Corn Planting or Milk moon). Illumination was 100% at midnight, will be 99% at noon and 98% at midnight tonight. Moonset was at 5:51 this morning. Moonrise is at 21:05 tonight. Moonset is at 6:45 tomorrow morning. Moonlight time is 8 hours, 46 minutes which is 29 minutes shorter than yesterday.  

Spring began on March 12th and runs for 84 days through June 3rd. Warm Spring began on April 13th and runs for 52 days through June 3rd. High temperatures in this period are usually in the 50s, 60s and 70s. Highs in the 80s and 90s occur infrequently. Mother's Day is in seven days. Armed Forces Day is in 13 days.