May 8: ORD

Today is May 8th. It's the 129th day of the year. 237 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 70 and 47.

On the warm side, in 1979 (O'Hare's warmest May 8th) the high was a near-record 90 degrees (tied with 1963 as O'Hare's warmest high of the date) with an above-record low of 68 (O'Hare's warmest low of the date). The record warmest low of 67 was set in 1963 at Midway. The record high of 91 was set in 1963 at Midway. In 2000 the high was 85 with a near-record low of 66. In 1993 the high was 85 with a low of 59. In 1990 the high was 81 with a low of 60. In 1988 the high was 85 with a low of 52, a 33 degree spread. The other warm highs were 85 in 2005, 84 in 2004 and 82 in 2007. 19 of the past 33 highs (58%) were in the: 60s (10) and 70s (9). On the warm side, eight highs (24%) were in the: 80s (7) and 90s (1). On the cool side, six highs (18%) were in the: 40s (1) and 50s (5). O'Hare's second warmest May 8th was in 1963 as the high was 90 (ties 1979 as O'Hare's warmest high of the date)  with a low of 67.

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 70 with a cold low of 34, a 36 degree spread. In 1976 the high was 64 with a cold low of 34, a 30 degree spread. In 1974 the high was a cold 45 with a low of 42, a three degree spread and cold day. In 1972 the high was a cold 44 with a low of 39, a five degree spread and cold day. In 1971 the high was 74 with a low of 41, a 33 degree spread. In 1970 the high was 86 with a low of 63, a hot day. In 1966 the high was a cold 45 with a low of 35, a cold day. In 1965 the high was 83 with a low of 61, a warm day. In 1964 the high was 79 with a warm low of 61, a warm day. In 1963 the high was 90 with a low of 67, a hot day. 1963 was also the year of the record high and record warmest low. In 1960 the high was a cold 41 with a low of 35, a six degree spread and cold day. 1960 was also the year of the record coldest high.

More recently, we had additional large spreads of 42 degrees in 2005 (85/43), 35 degrees in 2004 (84/49), 32 degrees in 1992 (72/40) and 31 degrees in 1981 (63/32). There were no small spreads of seven degrees or less from 1979 onward.
 
On the cool side, in 1983 (O'Hare's second coldest May 8th)  the high was 48 with the record low of 29. A year later, in 1984, the high was 51 with a low of 38. The other cold low was 32 in 1981. The other cool highs were 50 two years ago, in 2010 and 54 in 1980. The record coolest high of 42 was set in 1960 at Midway. 19 of the last 33 lows (58%) were in the 40s. O'Hare recorded six consecutive 40s lows from 2001 through 2006. Five lows (15%) were in the cold: 20s (1) and 30s (4). Nine lows (27%) were in the warm: 50s (6) and 60s (3). O'Hare's coldest May 8th was in 1960 as the high was 41 (O'Hare's coldest high of the date) with a low of 35, a six degree spread.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:08 and sunrise is at 5:39. Sunset is at 20:01 and twilight ends at 20:32. There's a total of 14 hours, 22 minutes of daylight today and 15 hours, 24 minutes between twilights. We gained three minutes of daylight from yesterday. Tomorrow twilight begins at 5:07 and sunrise is at 5:38. The moon is waning gibbous, having passed full three nights ago at 22:35 as the full Flower moon (a.k.a. Corn Planting or Milk moon). Illumination was 93% at midnight, will be 90% at noon and 86% at midnight tonight. Moonset was at 7:46 this morning. Moonrise is at 23:12 tonight. Moonset is at 8:53 tomorrow morning. Moonlight time is 8 hours, 34 minutes which is two minutes longer than yesterday. Moonlight time is at its least today.  

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 five days. Armed Forces Day is in 11 days.