April 13: ORD

Today is April 13th. It's the 104th day of the year. 262 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. 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 58 and the normal low is 38. I've calculated the 33-year averages at 58 and 38.

On the warm side, in 2006 (O'Hare's warmest April 13th) the high was 80 (O'Hare's warmest high of the date) with a low of 52. Twenty-five years before that, in 1981, the high was 79 with a low of 50. Four years later, in 1985, the high was 71 with a low of 54. In 1998 the high was 68 with a low of 55. The other warm highs were 73 in 1988 (our most recent 70s high) and 70 in 1983. The record high of 82 and record warmest low of 62 were set on the same warm day in 1941 at the University of Chicago. The record high of 82 was first set way back in 1887 adjacent to Lake Michigan. 28 of the past 33 highs (85%) were in the: 40s (8), 50s (12) and 60s (8). On the warm side, five highs were in the: 70s (4) and 80s (1). Tied with 1981 as O'Hare's second warmest April 13ths was: 1960 (high of 76 and low of 53) and 1968 (high of 71 and warmest low of the date of 58). O'Hare's other pre-1979 warm highs were 77 in 1977 and 72 in 1967. 

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 a warm 77 with a low of 47, a 30 degree spread and warm day. In 1976 the high was 69 with a low of 32, a 37 degree spread. In 1974 the high was a warm 71 with a low of 48, a warm day. In 1973 the low was a cold 26 degrees. In 1972 the high was a warm 70 with a low of 39, a 31 degree spread. In 1968 the high was 71 with a low of 58, a warm day. In 1967 the high was a warm 72 degrees. In 1964 the low was a warm 51 degrees. In 1962 the high was a cold 43 with a low of 30, a cold day. In 1960 the high was 76 with a low of 53, a warm day.

More recently, we had large spreads of 38 degrees in 2003 (67/29) and 41 degrees in 1988 (73/32). 

On the cold side, in 1980 (O'Hare's coldest April 13th) the high was 46 with a low of 24 (O'Hare's coldest low of the date). In 2008 the high was 42 (O'Hare's coldest high of the date) with a low of 32. O'Hare's only other 20s lows of the date were all 29 degrees, in: 1989, 2003 and 2004 (our most recent 20s low). The other cold highs were 43 in 1992, 46 in 2004 and 46 in 2009. The record low of 21 and record coldest high of 33 were set on the same cold day in 1950 at Midway. 18 of the last 33 lows (55%) were in the 30s. Four lows (12%) were in the cold 20s. O'Hare's second coldest April 13th was in 1962 as the high was 43 with a low of 30. 11 lows (33%) were in the warm: 40s (7) and 50s (4).

There was an instance of back-to-back years in which temperatures were just about as opposite as they can be. In 1980 the high was 46 with a low of 24, overall 13 degrees BELOW normal. Then in 1981 the high was 79 with a low of 50, overall 16.5 degrees ABOVE normal.


The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:46 and sunrise is at 6:15. Sunset is at 19:33 and twilight ends at 20:02. There's a total of 13 hours, 18 minutes of daylight today and 14 hours, 16 minutes between twilights. We gained three minutes of daylight from yesterday. Tomorrow twilight begins at 5:44 and sunrise is at 6:13. The moon reaches last quarter today at 5:50. Illumination was 52% at midnight, will be 47% at noon and 42% at midnight tonight. Moonrise was at 2:07 this morning. Moonset was at 12:15 this afternoon. Moonrise is at 2:44 tomorrow morning. Moonlight time is 10 hours, 8 minutes which is 22 minutes longer than yesterday. 

Spring began on March 12th and runs for 84 days through June 3rd. Warm Spring begins today, 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 usually occur infrequently. Earth Day is in nine days.