May 24: ORD

Today is May 24th. It's the 144th day of the year. 221 days remain. It's week 21 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.

According to the National Climatic Data Center (NCDC), the normal high is 73 and the normal low is 50. I've calculated the 32-year averages at 70 and 50.

On the warm side, last year, in 2010, the high was 91 with the new record low of 70. In 1991 the high was 85 with the former record warmest low of 68. In 1933 the low was 67 which was another former record warmest low. In 1989 the high was 86 with a low of 65. in 2007 the high was 88 with a low of 63. The record high of 93 was last tied in 1950, as it was originally set in 1921. 20 of the last 32 highs (63%) were in the: 60s (10) and 70s (10). Seven highs (22%) were in the warmer: 80s (6) and 90s (1). Five highs (15%) were in the cool: 40s (1) and 50s (4). Our most recent 50s high was 54 in 1999.

Yesterday (Mon. May 23) was the 4th warmest May 23 of the past 33 years with a high of 79 and low of 60. It finished ahead of 1989 (82/56) and 2000 (81/57). Two of the three warmest May 23 days occurred recently. These were the warmest which occurred last year (2010) at 89/62 and 2007 at 89/60. 1991 was also warmer at 82/66. On Sun. May 22, the high of 87 and low of 61 made it the second warmest May 22 behind 1991's 84 and 67. 2011 finished ahead of 1994 (89/58) and 1992 (83/63).

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 91 with a low of 64, a hot day. In 1976 the high was a cool 60 degrees. In 1975 the high was 85 with a low of 62, a warm day. In 1972 the high was a hot 86 with a low of 54, a 32 degree spread. In 1965 the high was 83 with a low of 53, a 30 degree spread. In 1961 the high was 80 with a low of 45, a 35 degree spread. In 1960 the high was a cool 60 degrees.

More recently, there were large spreads of 34 degrees in 1985 (78/44), 32 degrees in 1983 (76/44), 31 degrees in 1997 (84/53) and 31 degrees in 2006 (80/49).

On the cool side, in 1992 the high was 46 with the record low of 34. In 2001 the high was 60 with a low of 42. Two years earlier, in 1999, the high was 54 with a low of 48, a six degree spread. Two decades earlier, in 1979, the high was 62 with a low of 40. Other cool highs were 61 in 1982, 57 in 1995, 56 in 1987 and 56 in 1996. The record coolest high of 44 occurred back in 1925. 17 of the last 32 lows (84%) were in the: 40s (17) and 50s (10). One low was in the cold 30s. Four lows were in the warmer: 60s (3) and 70s (1).

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 4:52 and sunrise is at 5:25. Sunset is at 20:16 and twilight ends at 20:49. There's a total of 14 hours, 51 minutes of daylight today and 15 hours, 57 minutes between twilights. We a minute of daylight from yesterday. Tomorrow twilight begins at 4:51 and sunrise is at 5:24. The moon reaches last quarter today at 13:52. Illumination was 55% at midnight, will be 50% at noon and 46% at midnight tonight. Moonrise is at 1:07 this morning. Moonset is at 12:34 this afternoon. Moonrise is at 1:31 tomorrow morning. Moonlight time is 11 hours, 27 minutes which is 35 minutes longer than yesterday.

The warm part of Spring (Warm Spring) began on April 13. Warm Spring runs for 52 days, through June 3. High temperatures in this period are usually in the 50s, 60s and 70s. Warmer 80s and 90s occur infrequently. Memorial Day is in six days. -Bernie-