May 22: ORD

Today is May 22nd. It's the 143rd day of the year. 223 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. 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 72 and the normal low is 50. I've calculated the 33-year averages at 73 and 50.

On the warm side, in 1991 the high was 84 with a low of 67. Last year, in 2011, the high was 87 with a low of 61. In 1994 the high was 89 with a low of 58, a 31 degree spread. Two years earlier, in 1992, the high was 83 with a low of 63. The other warm high was 87 in 2007. The record high of 94 was set  back in 1925, at a time when the official readings were taken adjacent to Lake Michigan. The record warmest low of 75 was set in 1977 at Midway. 31 of the past 33 highs (94%) highs were in the: 60s (12), 70s (11) and 80s (8). Two highs were in the cool 50s. O'Hare's warmest May 22nd was in 1977 (O'Hare's warmest high of the date of 91 with its warmest low of the date of 70). O'Hare's second warmest May 22nd was in 1964 as the high was 89 with a low of 65. 

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 70, a hot day and year of the record warmest low. In 1975 the high was 83 with a low of 62, a warm day. In 1974 the low was a warm 64 degrees. In 1970 the high was a hot 86 with a low of 54, a 32 degree spread and hot day. In 1969 the high was a cool 54 with a low of 41, a cool day. In 1967 the high was a cool 57 with a low of 40, a cool day. In 1966 the high was 76 with a low of 43, a 33 degree spread. In 1964 the high was 89 with a low of 65, a hot day. In 1963 the high was 54 with a low of 35, a cool day. The low was colder than the record low. In 1962 the high was a warm 84 with a low of 51, a 33 degree spread. In 1961 the high was 60 with a low of 36, a cool day. The low was equal to the record low.

More recently, there was a small spread of seven degrees in 1998 (60/53). There were large spreads of 38 degrees in 1979 (75/37), 36 degrees in 1980 (82/46), 33 degrees in 1995 (78/45), 32 degrees in 2007 (87/55) and 31 degrees in 1993 (76/45).

On the cool side, in 2006 the high was 62 with the record low of 36. Three years earlier, in 2003, the high was 61 with a low of 39. The former record low was 37 in 1997. It was also 37 at O'Hare in 1979. O'Hare's other cold lows were 35 in 1963 and 36 in 1961. These were not official because O'Hare was not the official station of record for Chicago during these years. The other cool highs were 59 in 1986, 59 in 2008 and 60 in 1998. The record coolest high of 44 occurred back in 1917, at a time when the official readings were taken adjacent to Lake Michigan. 26 of the last 33 lows (79%) were in the: 40s (11) and 50s (15). O'Hare recorded 11 consecutive lows in the 40s & 50s from 1980 through 1990. Four lows (12%) were in the cold 30s. Three lows (9%) were in the warm 60s. O'Hare's coolest May 22nd was in 1963 as the high was its co-coolest of 54 (tied with 1969) and low of 35 (colder than the official record low).

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 4:53 and sunrise is at 5:26. Sunset is at 20:15 and twilight ends at 20:48. There's a total of 14 hours, 49 minutes of daylight today and 15 hours, 55 minutes between twilights. We gained a minute of daylight from yesterday. Tomorrow twilight begins at 4:52 and sunrise is at 5:25. The moon is waxing crescent, having passed new two nights ago at 18:47. Illumination was 2% at midnight, will be 3% at noon and 5% at midnight tonight. Moonrise was at 6:36 this morning. Moonset is at 21:53 tonight. Moonrise is at 7:28 tomorrow morning. Moonlight time is 15 hours, 17 minutes which is one minute 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. National Maritime Day is today. Memorial Day is in six days.