May 26: ORD

Today is May 26th. It's the 146th day of the year. 219 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 51. I've calculated the 32-year averages at 71 and 49.

On the warm side, last year, in 2010, the high was 87 with a low of 66. In 1985 the high was 89 with a low of 62. In 1991 the high was 82 with a low of 69. In 1987 the high was 86 with a low of 61. The record high of 94 was set back in 1911 and the record warmest low of 75 occurred in 1914. 22 of the past 32 highs (69%) were in the: 60s (9) and 70s (13). Six highs (19%) were in the warmer 80s. Four highs (12%) were in the cool 50s. Our most recent 50s high was 57 in 2001. There seems to be a distinction in terms of the eras of the 80s highs. The first three happened between 1985 and 1991. The second three happened between 2006 and last year, 2010. This year an 80 won't occur, in fact a cool 50s high is forecast.

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 87 with a low of 65, a hot day. In 1971 the high was a cool 54 with a low of 43, a cool day. In 1969 the high was 74 with a cold low of 39, a 35 degree spread. In 1967 the high was a hot 92 with a low of 61, a 31 degree spread and hot day. In 1966 the high was 82 with a low of 49, a 33 degree spread. In 1965 the low was a warm 63 degrees. In 1962 the high was a cool 59 degrees. In 1961 the high was 47 with a low of 36, a cold day and year of the record coolest high. In 1959 the high was 84 with a warm low of 64, a warm day.

More recently, there were large spreads of 36 degrees in 1988 (78/42), 36 degrees in 2002 (73/37), 34 degrees three years ago (in 2008) (81/47), 33 degrees in 1993 (78/45), 31 degrees in 1979 (70/39) and 31 degrees in 1998 (78/47).

On the cool side, in 1992 the high was 53 with a low of 35. In 1983 the high was 60 with the record low of 34. In 2001 the high was 57 with a low of 38. In 1994 the high was 59 with a low of 37. In 1997 the high was 55 with a low of 46. Another cool high was 60 in 1996. The other 30s lows were 37 in 2002 and 39 in 1979. The record coolest high of 48 occurred in 1961. 21 of the last 32 lows (66%) were in the: 40s (13) and 50s (8). Six lows (19%) were in the cold 30s. Our most recent 30s low was 37 in 2002. Five lows (15%) were in the warmer 60s.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 4:50 and sunrise is at 5:23. Sunset is at 20:18 and twilight ends at 20:51. There's a total of 14 hours, 55 minutes of daylight today and 16 hours, 1 minute between twilights. We gained two minutes of daylight from yesterday. Tomorrow twilight begins at 4:49 and sunrise is at 5:22. The moon is waning crescent, having reached last quarter two days ago at 13:52. Illumination was 36% at midnight, will be 32% at noon and 27% at midnight tonight. Moonrise is at 1:54 this morning. Moonset is at 14:33 this afternoon. Moonrise is at 2:18 tomorrow morning. Moonlight time is 12 hours, 39 minutes which is 36 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 four days.