April 19: ORD

Today is April 19th. It's the 110th day of the year. 256 days remain. It's week 16 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 61 and the normal low is 41. I've calculated the 33-year averages at 63 and 42.

On the warm side, in 1985 (O'Hare's warmest April 19th) the high was the record high of 86 with the record warmest low of 65. The former record warmest low of 62 occurred in 1948. Two decades later, in 2005, the high was 81 with a low of 60. In 1992 the high was 71 with a low of 61. In 1987 the high was 78 with a low of 50. In 2006 the high was 74 (our most recent 70s high) with a low of 52. In 1996 the high was 73 with a low of 51. The other warm highs were 79 in 2003 and 73 in 2004. 29 of the past 33 highs (88%) were in the: 50s (13), 60s (8) and 70s (8). On the warm side, two highs were in the 80s. O'Hare's third warmest April 19th was in 1977 as the high was 72 with a low of 62. On the cold side, two highs were in the: 30s (1) and 40s (1). 

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 48 degrees. In 1977 the high was 72 with a warm low of 62, a warm day. In 1975 the high was a cold 48 with a low of 41, a seven degree spread. 1973 the high was 69 with a warm low of 58, a warm day. In 1971 the high was a warm 73 with a low of 43, a 30 degree spread. In 1967 the high was a cold 48 degrees. In 1966 the high was 70 with a warm low of 54, a warm day. In 1964 the high was a cold 45 with a low of 41, a four degree spread. In 1962 the high was a cold 48 degrees. In 1961 the high was 60 with a low of 30, a 30 degree spread. In 1959 the high was a cold 41 with a low of 35, a six degree spread and cold day.

More recently, we had large spreads of 38 degrees in 2003 (79/41), 35 degrees in 2001 (68/33) and 31 degrees in 1979 (68/37). Other than last year, 2011 (see next section) there were no other small spreads.
 
On the cold side, in 1983 the high was 44 (O'Hare's only 40s high since 1979) with the record low of 22. Last year, in 2011, the high was 38 (O'Hare's only 30s high of the date) with a low of 34, a four degree spread. The other cold low was 28 in 1988. The record coldest high of 34 occurred back in 1904, at a time when the official readings were taken adjacent to Lake Michigan. 25 of the last 33 lows (76%) were in the: 30s (9) and 40s (16). Two lows (6%) were in the cold 20s. Six lows (18%) were in the warm: 50s (3) and 60s (3).

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:36 and sunrise is at 6:06. Sunset is at 19:40 and twilight ends at 20:09. There's a total of 13 hours, 34 minutes of daylight today and 14 hours, 33 minutes between twilights. We gained two minutes of daylight from yesterday. Tomorrow twilight begins at 5:34 and sunrise is at 6:04. The moon is waning crescent, heading towards new in two days at 2:18. Illumination was 4% at midnight, will be 2% at noon and 1% at midnight tonight. Moonrise was at 5:01 this morning. Moonset was at 18:27 tonight. Moonrise is at 5:28 tomorrow morning. Moonlight time is 13 hours, 26 minutes which is 33 minutes longer 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. Earth Day is in three days. Arbor Day is in eight days.