May 19: ORD

Today is May 19th. It's the 140th day of the year. 226 days remain. It's week 20 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 71 and the normal low is 49. I've calculated the 33-year averages at 71 and 49.

On the warm side, in 1996 (O'Hare's warmest May 19th) the high was 90 with the warmest and only 70s low of 72. Two years later, in 1998 (tied with 1975 as O'Hare's third warmest May 19th) the high was 91 with a low of 66. The other warm high was 83 in 1987. The record high of 94 was set in 1975 and tied in 1977. The record warmest low of 74 occurred back in 1911, at a time when the official readings were taken adjacent to Lake Michigan. 24 of the past 33 highs (73%) were in the: 60s (9) and 70s (15). O'Hare recorded eight consecutive 60s & 70s highs from 1988 through 1995. Six highs (18%) were in the warm: 80s (4) and 90s (2). O'Hare's warmest high of the date was 93 in 1977. O'Hare's second warmest May 19th was in 1962 with a high of 91 and very warm low of 69. 1975 is tied with 1998 as O'Hare's third warmest May 19th (high of 91, low of 66). Three highs (9%) were in the cool: 40s (1) and 50s (2).

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 93 with a low of 63, a hot day, 30 degree spread and year of the record high. In 1976 the high was 76 with a low of 39, a 37 degree spread. In 1975 the high was 91 with a low of 66, a hot day and year of the record high. In 1972 the high was a warm 83 degrees. In 1970 the high was a warm 85 with a low of 55, a 30 degree spread. In 1964 the high was a hot 86 with a low of 47, a 39 degree spread and warm day. In 1962 the high was 91 with a low of 69, a hot day. In 1960 the high was 67 with a warm low of 61, a six degree spread. In 1959 the high was 87 with a low of 63, a hot day.

More recently, we had large spreads of 38 degrees in 1985 (79/41), 34 degrees in 1992 (75/41), 32 degrees in 1987 (83/51), 30 degrees in 1988 (74/44), 30 degrees in 1995 (76/46) and 30 degrees last year, in 2010 (74/44).
 
On the cool side, in 2000 the high was 48 (O'Hare's only 40s high of the date) with a low of 44, a four degree spread. Two years later, in 2002, the high was 54 with a low of 38. 2000 and 2002 were O'Hare's coolest May 19th days. In 1986 the high was 55 with a low of 42. The record low of 36 was set in 1993, tying the original record low which was set way back in 1894. The record coolest high of 41 occurred way back in 1895, at a time when the official readings were taken adjacent to Lake Michigan. 19 of the last 33 lows (58%) were in the 40s. 12 lows (36%) were in the warm: 50s (9), 60s (2) and 70s (1). Two lows (6%) were in the cold 30s.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 4:55 and sunrise is at 5:28. Sunset is at 20:12 and twilight ends at 20:45. There's a total of 14 hours, 44 minutes of daylight today and 15 hours, 50 minutes between twilights. We gained two minutes of daylight from yesterday. Tomorrow twilight begins at 4:54 and sunrise is at 5:27. The moon is waning crescent. Illumination was 3% at midnight, will be 2% at noon and 1% at midnight tonight. Moonrise was at 4:32 this morning. Moonset is at 19:16 tonight. Moonrise is at 5:08 tomorrow morning. Moonlight time is 14 hours, 44 minutes which is 25 minutes longer 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. Armed Forces Day is today. National Maritime Day is in three days.