May 20: ORD

Today is May 20th. It's the 140th day of the year. 225 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.

According to the National Climatic Data Center (NCDC), the normal high is 71 and the normal low is 50. I've calculated the 31-year averages at 72 and 47.

On the warm side, in 2004 the high was 84 with the warmest and only 60s low of 63. Another high of note was 84 in 1992. Last year the high was 84 with a low of 61. The record high of 95 and record warmest low of 70 were set on the same day in 1977. 25 of 31 (81%) highs have been: 60s (10) and 70s (15). Four highs were in the warmer 80s. Two highs were in the cooler: 40s (1) and 50s (1).

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 78 with a low of 46, a 32 degree spread. In 1977 the high was 93 with a low of 64, a hot day and year of the record high and warmest low. In 1975 the high was 87 with a low of 67, another hot day. In 1972 the high was a hot 87 with a low of 54, a 33 degree spread. In 1970 the high was a warm 85 with a low of 52, a 33 degree spread. In 1965 the high was 74 with a low of 40, a 34 degree spread. In 1964 the high was a cool 58. In 1962 the high was a warm 85 with a low of 53, a 32 degree spread. In 1959 the low was a warm 64 degrees.

More recently, we had large spreads of 41 degrees in 1981 (76/35), 37 degrees in 1994 (78/41), 36 degrees in 2006 (74/38), 34 degrees in 1979 (78/44), 33 degrees in 1992 (84/51) and 31 degrees in 1980 (74/43).

On the cool side, in 2002 the high was 48 (the only 40s high) with the record low of 33 (former record low was 35 in 1981). In 1986 the high was 56 (only 50s high) with a low of 41. Other lows of note were 35 in 1981 and 38 in 2006. The record coolest high of 40 occurred way back in 1895. 25 of 31 (81%) lows were: 40s (16) and 50s (9). Four lows were in the colder 30s. Two lows were in the warmer 60s.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight began at 4:55 and sunrise was at 5:28. Sunset is at 20:13 and twilight ends at 20:45. There's a total of 14 hours, 45 minutes of daylight today and 15 hours, 50 minutes between twilights. Tomorrow twilight begins at 4:54 and sunrise is at 5:27. The moon reaches first quarter today at 18:43. Illumination was 42% at midnight, will be 47% at noon and 53% at midnight tonight. Moonset was at 1:10 this morning. Moonrise is at 12:14 this afternoon. Moonset is 1:38 in the morning tomorrow. Moonrise is at 13:27 tomorrow. Moonlight time is 12 hours, 56 minutes which is 42 minutes shorter than yesterday.

National Maritime Day is in two days and Memorial Day is in 11 days. - Bernie -