April 3: ORD

Today is April 3rd. It's the 94th day of the year. 272 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 35. I've calculated the 33-year averages at 56 and 36.

On the warm side, in 1981 (O'Hare's warmest April 3rd) the high was 75 with a low of 59. In 1999 the high was 73 with a low of 52. Two years earlier, in 1997, the high was 67 with a low of 52. The other warm highs were 72 last year (in 2011), 70 in 1996 and 70 in 2007. The other warm low was 49 two years ago, in 2010. The record high of 81 was set in 1956 at Midway. The record warmest low of 60 occurred back in 1928, at a time when the official readings were taken adjacent to Lake Michigan. 28 of the past 33 highs (85%) were in the: 40s (9), 50s (10) and 60s (9). Our most recent 40s high was 47 in 2003. Our most recent 60s high was 64 in 2005. On the warm side, five highs were in the 70s. Prior to 1979, O'Hare's warm highs were 72 in 1976, 70 in 1963 and 70 in 1978. The pre-1979 warm lows are 50 in 1974 and 48 in 1968.  

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 warm 70 with a low of 37, a 33 degree spread. In 1976 the high was a warm 72 with a low of 45, a warm day. In 1975 the high was 31 with a low of 19, a cold day. In 1974 the high was 65 with a warm low of 50, a warm day. In 1973 the high was 44 with a low of 38, a six degree spread. In 1971 the high was a cold 40 degrees with a low of 24, a cold day. In 1968 the low was a warm 48 degrees. In 1966 the high was a cold 40 degrees. In 1964 the high was a cold 38 degrees with a low of 27, a cold day. In 1963 the high was a warm 70 with a low of 39, a 31 degree spread. In 1961 the low was a cold 23 degrees. In 1960 the high was a cold 42 with a low of 37, a five degree spread.

More recently, we had a small spread of three degrees in 1983 (40/37). There were large spreads of 38 degrees in 1996 (70/32), 37 degrees in 1982 (62/25), 37 degrees last year, in 2011 (72/35), 35 degrees in 2007 (70/35), 33 degrees in 2005 (64/31) and 32 degrees in 2004 (59/27).

On the cold side, in 1987 the high was 40 with the record low of 17. The record low of 17 also occurred way back in 1879. In 1993 the high was 44 with a low of 22. The other cold highs were 40 (1983 and 2002) and 42 in 1984. The record coldest high of 30 was set in 1954 at Midway. 17 of the last 33 lows (52%) were in the 30s. Six lows (18%) were in the cold: 10s (a.k.a. teens) (1) and 20s (5). Our most recent 20s low is 27 in 2004. 1975 was O'Hare's coldest April 3rd with a high of 31 (O'Hare's coldest high of the date) and low of 19. The only other 30s high of the date was 38 in 1964. The low of 19 in 1975 and 17 in 1987 are O'Hare's only lows in the 10s (a.k.a. teens). Ten lows (30%) were in the warm: 40s (7) and 50s (3).

Today is a major day in Chicago's snow history. At O'Hare and Midway in 1975, this was the second day of a two day storm. At O'Hare, 0.4 inches of an 11.1 inch total occurred. At Midway, 0.4 inches of a 9.8 inch total occurred.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:03 and sunrise is at 6:32. Sunset is at 19:22 and twilight ends at 19:50. There's a total of 12 hours, 50 minutes of daylight today and 13 hours, 47 minutes between twilights. We gained two minutes of daylight from yesterday. Tomorrow twilight begins at 6:02 and sunrise is at 6:30. The moon is waxing gibbous and will reach full in three days as the full Pink moon at 14:19. Illumination was 83% at midnight, will be 87% at noon and 91% at midnight tonight. Moonset was at 4:23 this morning. Moonrise is at 16:02 this afternoon. Moonset is at 4:54 tomorrow morning. Moonlight time is 12 hours, 21 minutes which is 39 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 three days. Easter is in five days.