May 2: ORD

Today is May 2nd. It's the 123rd day of the year. 243 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. Before this, the official site of record was on the south side of Chicago at Midway International Airport (MDW), beginning on Wednesday, July 1, 1942. From Friday, January 1, 1926 through Tuesday, June 30, 1942, the official site was at the University of Chicago. Before that, the official site was at various locations in Chicago going back to Monday, October 16, 1871. Observations taken from October 15, 1870 to October 8, 1871 were lost in the Great Chicago Fire.

According to the National Climatic Data Center (NCDC), the normal high is 66 and the normal low is 44. I've calculated the 33-year averages at 64 and 43.

On the warm side, in 2001 (O'Hare's second warmest May 2nd) the high was 81 with the record warmest low of 65. In 1992 the high was 76 with a low of 50. The record high of 91 was set in 1959 at Midway. 31 of the past 33 highs (94%) were in the: 50s (12), 60s (9) and 70s (10). On the warm side, one high was in the 80s. O'Hare's warmest May 2nd was in 1959 as the high was 89 (O'Hare's warmest high) with a low of 61. O'Hare also had highs of 84 in 1965 and 1969. On the cold side, one high was in the 40s. O'Hare has recorded just three highs in the 40s for the date: 44 in 2005, 46 in 1970 and 49 in 1967.

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 55 with a cold low of 29, a cold day. In 1976 the high was a cool 54 degrees. In 1971 the high was a cool 50 with a low of 35, a cold day. In 1970 the high was a cold 46 with a low of 39, a seven degree spread and cold day. In 1969 the high was a warm 84 with a low of 55, a warm day. In 1968 the high was a warm 85 with a low of 35, a huge 50 degree spread. Spreads of 50 degrees or more are extremely rare. In 1967 the high was a cold 49 with a low of 36, another cold day. In 1966 the high was 58 with a cold low of 28 (just a degree above the record low), a 30 degree spread and cold day. In 1965 the high was a warm 84 with a low of 49, a 35 degree spread and warm day. In 1961 the low was a cold 31 degrees. In 1959 the high was 89 with a low of 61, a hot day. And yes, 1959 (see above) was the year of the record high.

More recently, we had no small spreads. The large spreads were 38 degrees in 1982 (76/38), 36 degrees in 1988 (75/39), 31 degrees in 1999 (73/42), 31 degrees in 1980 (75/44) and 30 degrees in 1990 (68/38).

On the cool side, in 2005 (O'Hare's coldest May 2nd) the high was 44 (O'Hare's coldest high of the date) with a low of 35. In the prior year of 2004 (O'Hare's second coldest May 2nd), the high was 51 with a low of 32. The other cool highs were 50 in 1989, 53 in 2002, 53 in 2003 and 54 in 1997. The record low of 27 was set way back in 1875, at a time when the official readings were taken adjacent to Lake Michigan. The record coldest high of 37 occurred back in 1940 at the University of Chicago. 17 of the last 33 lows (52%) were in the 40s. Nine lows (27%) were in the cold 30s. Our most recent 30s low was 35 in 2005. O'Hare has recorded just four lows of 32 degrees or lower. Three of them occurred prior to 1979. They are 28 in 1966, 29 in 1978 and 31 in 1961. Seven lows (21%) were in the warm: 50s (6) 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 begins at 5:16 and sunrise is at 5:47. Sunset is at 19:54 and twilight ends at 20:25. There's a total of 14 hours, 7 minutes of daylight today and 15 hours, 9 minutes between twilights. We gained two minutes of daylight from yesterday. Tomorrow twilight begins at 5:15 and sunrise is at 5:46. The moon is waxing gibbous. Illumination was 79% at midnight, will be 84% at noon and 88% at midnight tonight. Moonset was at 3:21 this morning. Moonrise was at 16:02 this afternoon.  Moonset is at 3:52 tomorrow morning. Moonlight time is 11 hours, 19 minutes which is 41 minutes shorter than yesterday.  

Spring began on March 12th and runs for 84 days through June 3rd. Warm Spring began on April 13th and runs for 52 days through June 3rd. High temperatures in this period are usually in the 50s, 60s and 70s. Highs in the 80s and 90s occur infrequently. Mother's Day is in 11 days.