March 20: ORD

Today is March 20th. It's the 80th day of the year. 286 days remain. It's week 12 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 48 and the normal low is 31. I've calculated the 33-year averages at 47 and 30.

On the warm side, in 2003 the high was 65 with a low of 43. In 1994 the high was 61 with a low of 39. A year later, in 1995, the high was 60 with a low of 40. The other warm highs were 62 in 2004 (our most recent 60s high) and 61 in 1991. The other warm low was 43 in 2000. The record high of 76 was set back in 1921 and the record warmest low of 53 occurred back in 1918. Both records were set at a time when the official readings were taken adjacent to Lake Michigan. By the way, the record high and record warmest lows were shattered this year (in 2012) as the high reached 85 with a low of 63. 27 of the past 33 highs (82%) were in the: 30s (8), 40s (12) and 50s (7). On the warm side, five highs were in the 60s. Until this year (2012), O'Hare's warmest March 20th was in 1976 when the high was 70 (still O'Hare's only 70s high) with a low of 47 (which was O'Hare's warmest low of the date). The other pre-1979 warm highs were 69 in 1972 and 60 in 1975. 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 1976 the high was 70 with a low of 47, a warm day. In 1975 the high was a warm 60 degrees. In 1972 the high was a warm 69 with a low of 38, a 31 degree spread and warm day. In 1970 the high was 41 with a low of 36, a five degree spread. In 1967 the high was a cold 36 with a low of 33, a three degree spread. In 1966 the high was 56 with a low of 26, a 30 degree spread. In 1965 the high was 22 with a low of 0, a cold day. In 1960 the high was a cold 34 with a low of 20, a cold day.

More recently, we had small spreads of three degrees in 1998 (36/33), five degrees in 1983 (32/27) and seven degrees in 1993 (38/31). There was a large spread of 30 degrees in 2004 as the high was 62 with a low of 32.

On the cold side, in 1986 the high was 26 with a low of 8. Two years later, in 1988, the high was 36 with a low of 20. The other cold highs were 32 in 1983 and 36 in 1998. The record low of 4 and record coldest high of 15 were set on the same cold day way back in 1885, at a time when the official readings were taken adjacent to Lake Michigan. 28 of the last 33 lows (85%) were in the: 20s (15) and 30s (13). One low was in the cold single digits. Four lows were in the warm 40s. O'Hare has never had a low in the 10s (a.k.a. teens) on March 20th. O'Hare's coldest March 20th was in 1965 when the high was 22 and low was 0.

Today is a major day in Chicago's snow history. At O'Hare in 1965, this was the first of seven days in which a total of 10.2 inches fell. Today just a tenth of an inch fell. At O'Hare in 1983, this was the second day of a three day, 7.2 inch snowstorm. Today 3.3 inches fell.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:28 and sunrise is at 6:56. Sunset is at 19:06 and twilight ends at 19:34. There's a total of 12 hours, 10 minutes of daylight today and 13 hours, 6 minutes between twilights. We gained two minutes of daylight from yesterday. Tomorrow twilight begins at 6:26 and sunrise is at 6:54. The moon is waning crescent and will be new in two mornings at 9:37. Illumination was 6% at midnight, will be 4% at noon and 2% at midnight tonight. Moonrise is at 5:40 this morning. Moonset is at 17:33 this afternoon. Moonrise is at 6:06 tomorrow morning. Moonlight time is 11 hours, 53 minutes which is 34 minutes longer than yesterday. The Spring Equinox is at 0:14 this morning.

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. April Fools' Day and Palm Sunday are in 12 days.