May 11: ORD

Today is May 11th. It's the 131st day of the year. 234 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.

According to the National Climatic Data Center (NCDC), the normal high is 68 and the normal low is 46. I've calculated the 32-year averages at 70 and 48.

On the warm side, in 1982 the high was the record high of 89 degrees with a low of 58, a 31 degree spread. Three years later, in 1985, the high was 87 with a low of 60. In 1992 the high was 84 with a low of 61. Five years prior, in 1987, the high was 88 with a low of 53, a 35 degree spread. In 1991 the high was 85 with a low of 56. Other 80s highs were 82 in 2004 (our most recent 80s high) and 80 in 1986. Six of the highs in the 80s occurred between 1982 and 1992. 2004 was the lone exception. Another upper 50s low was 58 in 2000. The record warmest low of 70 occurred way back in 1881. 26 of the last 32 highs (81%) were in the: 60s (8), 70s (11) and 80s (7). On the cool side, six highs were in the: 40s (1) and 50s (5).

In looking back through the years to the first May at O'Hare in 1959, the following instances were notable: In 1978 the high was 66 with a warm low of 59, a seven degree spread. In 1977 the high was 73 with a low of 39, a 34 degree spread. In 1972 the high was 73 with a low of 42, a 31 degree spread. In 1971 the high was 74 with a low of 44, a 30 degree spread. In 1967 the high was a cool 55 degrees. In 1966 the high was 45 with a low of 34, a cold day. In 1963 the high was a cool 53 degrees. In 1961 the high was 77 with a low of 44, a 33 degree spread. In 1960 the high was a cold 46 with a low of 37, a cold day.

More recently, we had large spreads of 33 degrees in 1983 (73/40), 30 degrees in 1986 (80/50) and 30 degrees in 1988 (75/45).

On the cool side, in 1981 the high was 45 (our only 40s high) with the record low of 33. 15 years later, in 1996, the high was 52 with a low of 38. The other 30s lows were 39 two years ago (in 2009), 38 in 2006, 37 in 1990 and 36 in 1989. The record coldest high of 41 occurred way back in 1907. 24 of the last 32 lows (75%) were in the: 40s (13) and 50s (11). Six lows were in the cold 30s. Two lows were in the warmer 60s.

Today is a major day in Chicago's snow history. In 1966, O'Hare recorded 1.6 inches of snow. Rockford had an inch.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight is at 5:05 and sunrise is at 5:37. Sunset is at 20:03 and twilight ends at 20:35. There's a total of 14 hours, 26 minutes of daylight today and 15 hours, 30 minutes between twilights. We gained two minutes of daylight from yesterday. Tomorrow twilight begins at 5:04 and sunrise is at 5:36. The moon is waxing gibbous, having reached first quarter yesterday at 15:33. Illumination was 55% at midnight, will be 60% at noon and 66% at midnight tonight. Moonset is at 1:55 this morning. Moonrise is at 13:27 this afternoon. Moonset is at 2:24 tomorrow morning. Moonlight time is 12 hours, 28 minutes which is 42 minutes shorter 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. Armed Forces Day is in ten days. -Bernie-