April 9: ORD

Today is April 9th. It's the 100th day of the year. 266 days remain. It's week 15 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 56 and the normal low is 37. I've calculated the 33-year averages at 52 and 34.

On the warm side, in 1994 the high was 67 with a low of 48. Last year, in 2011, the high was 66 with a low of 44. The other warm highs were 72 in 1987, 68 in 1988 and 68 in 2005. The record high of 80 was set way back in 1887. The record warmest low of 58 occurred back in 1922. Both records were set at a time when the official readings were taken adjacent to Lake Michigan. 25 of the past 33 highs (76%) were in the: 40s (10) and 50s (15). O'Hare recorded seven consecutive 40s & 50s highs from 1998 through 2004. On the warm side, six highs (18%) were in the: 60s (5) and 70s (1). O'Hare's warmest April 9th was in 1967 as the high was 75 with a low of 49. O'Hare's warmest low of the date came on another 70 degree April 9th, in 1969. In 1969 the high was 71 with a low of 52. On the cold side, two highs (6%) were in the 30s. Prior to 1989 (high of 37, see "cold side" below), O'Hare's coldest highs were 37 in 1960, 37 in 1961 and 39 in 1975.  

In looking back through the years to the first April at O'Hare in 1959, the following instances were notable: In 1977 the high was 63 with a low of 29, a 34 degree spread. In 1976 the high was 60 with a low of 28, a 32 degree spread. In 1975 the high was a cold 39 with a low of 33, a six degree spread. In 1974 the low was a cold 25 degrees. In 1973 the high was a cold 41 degrees. In 1972 the high was 43 with a low of 24, a cold day. In 1969 the high was 71 with a low of 52, a warm day. In 1967 the high was 75 with a low of 49, a warm day. In 1964 the high was 56 with a cold low of 25, a 31 degree spread. In 1963 the high was a cold 44 degrees. In 1961 the high was a cold 37 with a low of 33, a four degree spread. In 1960 the high was 37 with a low of 25, a cold day. In 1959 the high was a cold 43 degrees.

More recently, we had small spreads of four degrees in 1998 (45/41) and seven degrees in 1980 (40/33). The large spreads were 45 degrees in 1987 (72/27),  33 degrees in 2005 (68/35) and 30 degrees in 1988 (68/38).
 
On the cold side, in 1989 (O'Hare's coldest April 9th) the high was 37 with the record low of 20. In 1997 the high was 38 with a low of 22. In 1985 the high was 42 with a low of 21. In 1979 the high was 40 with a low of 26. In 1982 the high was 40 with a low of 27. The other cold highs were 40 in 1980, 42 in 1995, 43 in 2003 and 43 in 2007. The record coldest high of 33 occurred way back in 1874, at a time when the official readings were taken adjacent to Lake Michigan. 27 of the last 33 lows (82%) were in the: 20s (10) and 30s (17). Six lows were in the warm 40s.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:53 and sunrise is at 6:22. Sunset is at 19:29 and twilight ends at 19:57. There's a total of 13 hours, 7 minutes of daylight today and 14 hours, 4 minutes between twilights. We gained two minutes of daylight from yesterday. Tomorrow twilight begins at 5:51 and sunrise is at 6:20. The moon is waning gibbous, having reached the full Pink (a.k.a. Sprouting Grass/Egg/Fish) moon three days ago at 14:19. Illumination was 91% at midnight, will be 88% at noon and 83% at midnight tonight. Moonset is at 8:05 this morning. Moonrise is at 23:28 tonight. Moonset is at 9:01 tomorrow morning. Moonlight time is 8 hours, 37 minutes which is 22 minutes shorter than yesterday. Moonlight time is at its least today.

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. Earth Day is in 13 days.