May 1: ORD

Today is May 1st. It's the 121st day of the year. 244 days remain. It's week 18 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 65 and the normal low is 42. I've calculated the 31-year averages at 63 and 43.

On the warm side, in 2001 the high was 83 with a low of 62. Six years later, in 2007, the high was 83 with a low of 50, a 33 degree spread. In 1992 the high was 88 with a low of 41, a huge 47 degree spread. Another warm low was 54 in 2006. The record high of 90 occurred in 1951. The record warmest low of 68 was set way back in 1899. 22 of the last 31 highs were: 50s (10) and 60s (12). On the warmer side, seven highs were: 70s (4) and 80s (3). On the cooler side, two highs were in the 40s.

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 a cold 49 with a low of 32, a cold day. In 1977 the high was a warm 78. In 1973 the high was 75 with a low of 60, a warm day. In 1966 the high was 48 with a low of 31, a cold day. In 1965 the high was a hot 87 with a low of 44, a huge 43 degree spread and warm day.

More recently, we had a small spreads of five degrees in 2004 (48/43) and in 2006 (59/54). The large spreads were 33 degrees in 1999 (72/39), 32 degrees in 1987 (70/38) and 31 degrees in 1988 (68/37).

On the cool side, no days were significantly below normal (11.5 degrees or more below normal mean). However, the record low of 30 occurred in 1979. The cool highs were 48 in 2004, 49 in 2005 and 53 in 1995. The record coldest high of 38 was set back in 1909. 27 of the last 31 lows were: 30s (12) and 40s (15). Four lows were in the warmer: 50s (3) and 60s (1).

Today is a major day in Chicago's snow history. 1940 holds the record for the latest two inches or more. According to the record, 2.2 inches of snow fell in Chicago between the 1st, 2nd and 3rd. There is no indication of how much fell on what day. Tom Skilling says that 3.7 inches fell at the University of Chicago on the 1st and 2nd. Rockford had a total of 2 inches of snow (1.5 on the 1st and 0.5 on the 2nd).

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight began at 5:18 and sunrise was at 5:49. Sunset is at 19:53 and twilight ends at 20:23. There's a total of 14 hours, 4 minutes of daylight today and 15 hours, 5 minutes between twilights. Tomorrow twilight begins at 5:17 and sunrise is at 5:47. The moon is waning gibbous. Illumination was 91% at midnight, will be 88% at noon and 85% at midnight tonight. Moonset was at 7:45. Moonrise is at 23:41. Moonset is at 8:42 tomorrow. Moonlight time is 8 hours, 4 minutes which is 2 minutes shorter than yesterday.

National Teacher Day is in four days. Mother's Day is in eight days. - Bernie -