April 26: ORD

Today is April 26th. It's the 117th day of the year. 249 days remain. It's week 17 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 63 and the normal low is 42. I've calculated the 33-year averages at 65 and 43.

On the warm side, in 1990 (O'Hare's warmest April 26th by just half a degree) the high was 85 with a low of 66 (O'Hare's warmest low of the date). Four years later, in 1994, the high was 87 (our most recent 80s high) with a low of 63. Those 60s lows in 1990 and 1994 are the only 60s lows for the date. In 1986 the high was the record high of 89 with a low of 55, a 34 degree spread. Two years earlier, in 1984, the high was 83 with a low of 51, a 32 degree spread. The other warm highs were 82 in 1983, 78 three years ago (in 2009) and 76 in 2001. Note that all five of O'Hare's post-1978 80s highs occurred in a 12-year span from 1983 through 1994. The record warmest low of 69 occurred back in 1915, at a time when the official readings were taken adjacent to Lake Michigan. 23 of the past 33 highs (70%) were in the: 50s (11) and 60s (12). O'Hare recorded consecutive 50 & 60s highs as follows: six from 1995 through 2000 and seven from 2002 through 2008. On the warm side, nine highs (27%) were in the: 70s (4) and 80s (5). O'Hare's only pre-1983 80s high was 85 degrees in 1962. On the cold side, one high (3%) was in the 40s.

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 65 with a low of 35, a 30 degree spread. In 1976 the high was a cold 49 with a low of 33, a cold day. In 1974 the high was a warm 79 with a low of 45, a 34 degree spread. In 1972 the high was 62 with a cold low of 30, a 32 degree spread. In 1970 the high was a warm 78 degrees. In 1969 the high was a warm 79 with a low of 51, a warm day. In 1967 the high was a cold 47 with a low of 33, a cold day. In 1965 the high was a cold 44 with a low of 37, a seven degree spread and cold day. In 1963 the high was 69 with a low of 37, a 32 degree spread. In 1962 the high was 85 with a low of 57, a warm day. In 1959 the high was a cold 48 degrees.

More recently, we had a small spread of six degrees in 1995 (53/47). We had additional large spreads of 41 degrees in 1983 (82/41), 37 degrees in 2006 (64/27), 35 degrees three years ago, in 2009 (78/43), 30 degrees in 1997 (65/35) and 30 degrees in 2001 (76/46).
 
On the cool side, in 1980 (tied with 1967 (47/33) as O'Hare's coldest April 26th)) the high was 50 with a low of 30 (the previous record low). In 1993 (tied with 1965 (44/37) as O'Hare's second coldest April 26th)) the high was 47 with a low of 34. That high of 44 in 1965 is O'Hare's coldest high of the date. In 2006 the current record low of 27 was set. The record coldest high of 38 occurred back in 1907, at a time when the official readings were taken adjacent to Lake Michigan. 28 of the last 33 lows (85%) were in the: 30s (11) and 40s (17). O'Hare recorded 11 consecutive lows in the 30s & 40s from 1995 through 2005. O'Hare's coldest low (and tied with 1980) was 30 in 1972. One low was in the cold 20s (the record set in 2006). Four lows were in the warm: 50s (2) and 60s (2). O'Hare's third coldest April 26th was in 1976 (high of 49, low of 33).

There was an instance of back-to-back years in which temperatures were just about as opposite as they can be. In 1993 the high was 47 with a low of 34, overall 12.5 degrees BELOW normal. Then in 1994 the high was 87 with a low of 63, overall 22 degrees ABOVE normal.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:25 and sunrise is at 5:55. Sunset is at 19:48 and twilight ends at 20:18. There's a total of 13 hours, 53 minutes of daylight today and 14 hours, 53 minutes between twilights. We gained three minutes of daylight from yesterday. Tomorrow twilight begins at 5:23 and sunrise is at 5:54. The moon is waxing crescent. Illumination was 21% at midnight, will be 25% at noon and 29% at midnight tonight. Moonrise was at 9:32 this morning. Moonset is at 0:38 tomorrow morning. Moonrise is at 10:30 tomorrow morning. Moonlight time is 14 hours, 28 minutes which is 48 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. Arbor Day is tomorrow. May Day is in five days. Mother's Day is in 17 days.