April 2: ORD

Today is April 2nd. It's the 93rd day of the year. 273 days remain. It's week 14 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. 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 54 and the normal low is 34. I've calculated the 33-year averages at 56 and 36.

On the warm side, two years ago, in 2010, the high was 81 (just short of the record) with a low of 59. In 1999 the high was 75 with a low of 53. In 1981 the high was 80 with a low of 37, a 43 degree spread. The other warm highs were 72 in 2003, 70 in 1994 and 69 in 1997. The record high of 82 was set in 1963 and the record warmest low of 62 occurred in 1956. Both records were set at Midway. 21 of the past 33 highs (64%) were in the: 50s (14) and 60s (7). On the warm side, five highs (15%) were in the: 70s (3) and 80s (2). 1963 was O'Hare's warmest April 2nd as the high was 82 with a low of 61. The other pre-1979 warm highs were 73 in 1977, 72 in 1967 and 71 in 1974. On the cold side, seven highs (22%) were in the: 30s (4) and 40s (3). 

In looking back through the years to the first April at O'Hare in 1959, the following instances were notable: In 1978 the high was a cold 38 with a low of 31, a seven degree spread. In 1977 the high was a warm 73 with a low of 42, a 31 degree spread and warm day. In 1976 the high was 64 with a low of 34, a 30 degree spread. In 1975 the high was a cold 34 with a low of 27, a seven degree spread and cold day. In 1974 the high was a warm 71 with a low of 38, a 33 degree spread. In 1973 the high was 47 with a low of 40, a seven degree spread. In 1972 the high was a cold 40 degrees. In 1971 the high was a cold 39 degrees. In 1970 the high was a cold 38 with a low of 32, a six degree spread. In 1967 the high was a warm 72 with a low of 44, a warm day. In 1965 the high was a cold 39 degrees. In 1963 the high was 82 with a low of 61, a warm day and year of the record high. In 1962 the high was a cold 40 degrees. In 1961 the high was 44 with a low of 20, a cold day.

More recently, we had small spreads of four degrees in 1983 (40/36), five degrees in 1979 (37/32) and five degrees in 1990 (40/35). There were large spreads of 36 degrees in 2003 (72/36), 33 degrees in 1997 (69/36), 30 degrees in 1994 (70/40) and 30 degrees in 2001 (60/30).

On the cold side, in 1987 (O'Hare's coldest April 2nd) the high was 37 with a low of 21. In 1993 the high was 38 with a low of 24. The year prior, in 1992, the high was 38 with a low of 25. The other cold highs were 37 in 1979, 40 in 1983 and 40 in 1990. The record low of 18 was first set way back in 1896 and tied just three years later in 1899. The record coldest high of 30 was set back in 1936. Both records were set at a time when the official readings were taken adjacent to Lake Michigan. 19 of the last 33 lows (58%) were in the 30s. Six lows (18%) were in the cold 20s. O'Hare's second coldest April 2nd was in 1975 when the high was a cold 34 (O'Hare's coldest high of the date) with a low of 27. The other pre-1979 cold day was in 1961 when the high was 44 with a low of 20, O'Hare's coldest low of the date. Eight lows (24%) were in the warm: 40s (6) and 50s (2).

Today is a major day in Chicago's snow history. In 1970, it was the second day of a two day storm. At O'Hare, 4.0 inches of a 7.2 inch total occurred. At Midway, 2.5 inches of a 10.7 inch total occurred. And in Rockford, 2.8 inches of a 6.7 inch total occurred. At O'Hare and Midway in 1975, it was the first day of a two day storm. At O'Hare, 10.7 inches of an 11.1 inch total occurred. At Midway, 9.4 inches of a 9.8 inch total occurred. Rockford had 4.6 inches today in 1975.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:05 and sunrise is at 6:33. Sunset is at 19:21 and twilight ends at 19:49. There's a total of 12 hours, 48 minutes of daylight today and 13 hours, 44 minutes between twilights. We gained three minutes of daylight from yesterday. Tomorrow twilight begins at 6:03 and sunrise is at 6:32. The moon is waxing gibbous. Illumination was 74% at midnight, will be 79% at noon and 83% at midnight tonight. Moonset was at 3:52 this morning. Moonrise is at 14:52 this afternoon. Moonset is at 4:23 tomorrow morning. Moonlight time is 13 hours which is 34 minutes shorter than yesterday.

Spring began on March 12th and runs for 84 days through June 3rd. Cool Spring began on March 12th and runs for 32 days through April 12th. High temperatures in this period are usually in the 30s, 40s and 50s. Highs in the 60s and 70s usually occur infrequently. Good Friday is in four days. Easter is in six days.