March 13: ORD

Today is March 13th. It's the 73rd day of the year. 293 days remain. It's week 11 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 45 and the normal low is 28. I've calculated the 33-year averages at 46 and 30.

On the warm side, in 1990 (O'Hare's warmest March 13th) the high was 72 (a former record high) with the record warmest low of 62. Five years later, in 1995, the high was 72 (another former record high) with a low of 51. In 2007 the high was the record high of 73 with a low of 48. The other warm highs were 63 in 2006, 59 in 2002, 58 in 1996 and 57 in 2008. The other warm low was 41 two years ago, in 2010. 28 of the past 33 highs (85%) were in the: 30s (11), 40s (9) and 50s (8). On the warm side, four highs were in the: 60s (1) and 70s (3). O'Hare's pre-1979 warm highs were 62 in 1973 and 59 in 1964. On the cold side, one high was in the 20s.

In looking back through the years to the first March at O'Hare in 1959, the following instances were notable: In 1978 the high was 37 with a low of 31, a six degree spread. In 1977 the high was 50 with a warm low of 43, a seven degree spread. In 1975 the high was 31 with a low of 16, a cold day. In 1973 the high was a warm 62 degrees. In 1972 the high was 37 with a low of 30, a seven degree spread. In 1970 the high was a cold 33 degrees. In 1968 the high was 38 with a cold low of 13 degrees, a cold day. In 1967 the high was 40 with a low of 35, a five degree spread. In 1964 the high was a warm 59 degrees. In 1962 the high was 34 with a low of 29, a five degree spread. In 1961 the high was 42 with a low of 35, a seven degree spread. In 1960 the high was a cold 28 with a low of 17, a cold day.

More recently, we had small spreads of four degrees two years ago, in 2010 (45/41), six degrees in 1985 (38/32), six degrees in 1987 (37/31) and seven degrees in 1991 (36/29). The large spreads were 31 degrees in 1983 (54/23) and 33 degrees in 2006 (63/30).

On the cold side, in 1993 (O'Hare's coldest March 13th) the high was 22 (O'Hare's only 20s high) with a low of 11 (O'Hare's coldest low of the date). In 2005 the high was 33 (our most recent 30s high) with a low of 13. The other cold highs were 31 in 1988, 32 in 1980 and 33 in 1984. The record low of 6 was set way back in 1896, at a time when the official readings were taken adjacent to Lake Michigan. The record coldest high of 21 occurred way back in 1888, also at a time when the official readings were taken adjacent to Lake Michigan. 22 of the last 33 lows (67%) were in the: 20s (8) and 30s (14). O'Hare recorded 12 consecutive lows in the 20s & 30s from 1978 through 1989. Seven lows (21%) were in the cold 10s (a.k.a. teens). On the warm side, four lows (12%) were in the: 40s (2), 50s (1) and 60s (1).

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:40 and sunrise is at 7:08. Sunset is at 18:58 and twilight ends at 19:26. There's a total of 11 hours, 50 minutes of daylight today and 12 hours, 46 minutes between twilights. We gained three minutes of daylight from yesterday. Tomorrow twilight begins at 6:38 and sunrise is at 7:06. The moon is waning gibbous and reaches last quarter tomorrow at 20:25. Illumination was 70% at midnight, will be 65% at noon and 59% at midnight tonight. Moonrise is at 0:37 this morning. Moonset is at 10:14 this morning. Moonrise is at 1:42 tomorrow morning. Moonlight time is 9 hours, 37 minutes which is 12 minutes longer than yesterday.

Spring began on March 12th (yesterday) and runs for 84 days through June 3rd. Cool Spring began on March 12th (yesterday) 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. St. Patrick's Day is in four days.