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 32-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. Other warm lows were 58 last year (in 2010) and 54 in 2006. The record high of 90 was set in 1951. The record warmest low of 68 occurred way back in 1899. 22 of the last 32 highs (69%) were in the: 50s (10) and 60s (12). On the warmer side, eight highs were in the: 70s (5) and 80s (3). On the cold 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 degrees. In 1973 the high was 75 with a warm low of 60, a warm day. In 1966 the high was a cold 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. In 1963 the low was a cold 29 degrees, a temperature that is colder than the official record low of 30. In 1959 the high was 75 with a low of 41, a 34 degree spread.

More recently, we had a small spreads of five degrees in both 2004 (48/43) and 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, in 2005 the high was 49 with a low of 35. In 1979 the high was 57 with a low of 30. Since O'Hare was not the station of record in 1979, the official record low of 30 was set in 1943. Other cool highs were 48 in 2004 and 53 in 1995. The record coldest high of 38 occurred back in 1909. 27 of the last 32 lows (84%) were in the: 30s (12) and 40s (15). Five lows were in the warmer: 50s (4) 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, WGN-TV, 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 is at 5:19 and sunrise is at 5:49. Sunset is at 19:52 and twilight ends at 20:23. There's a total of 14 hours, 3 minutes of daylight today and 15 hours, 4 minutes between twilights. We gained three minutes of daylight from yesterday. Tomorrow twilight begins at 5:17 and sunrise is at 5:48. The moon is waning crescent. Illumination was 4% at midnight, will be 2% at noon and 1% at midnight tonight. Moonrise is at 4:39 this morning. Moonset is at 18:42 tonight. Moonrise is at 5:07 tomorrow morning. Moonlight time is 14 hours, 3 minutes which is 35 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. National Teacher Day is in two days. Mother's Day is in seven days. -Bernie-