March 12: ORD

Today is March 12th. It's the 72nd day of the year. 294 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 45 and 26.

On the warm side, in 1990 (O'Hare's warmest March 12th) the high was the record high of 81 with the record warmest low of 59. Five years later, in 1995, the high was 71 with a low of 41, a 30 degree spread. In 1982 the high was 60 with a low of 36. In 2006 the high was 56 with a low of 40. Two years ago, in 2010, the high was 55 with a low of 40. The other warm highs were 63 in 2007, 60 in 1981 and 57 in 1994. 24 of the past 33 highs (73%) were in the: 30s (9), 40s (9) and 50s (6). Our most recent 30s high was 34 in 2005. On the warm side, five highs (15%) were in the: 60s (3), 70s (1) and 80s (1). Until 1990, O'Hare's warmest March 12th occurred in 1977 when the high was 69 with a low of 43. Prior to 1979, the other warm high was 60 in 1976. On the cold side, four highs (12%) were in the 20s. Prior to 1984, O'Hare hadn't had a high in the 20s (they were all 30 degrees or higher).

In looking back through the years to the first March at O'Hare in 1959, the following instances were notable: In 1977 the high was 69 with a low of 43, a warm day. In 1976 the high was a warm 60 degrees. In 1969 the low was a cold 11 degrees. In 1968 the high was a cold 33 degrees. In 1967 the high was 38 with a low of 33, a five degree spread. In 1966 the low was a warm 40 degrees. In 1965 the high was 34 with a low of 29, a five degree spread. In 1962 the high was 37 with a low of 33, a four degree spread. In 1960 the high was 33 with a low of 10, a cold day.

More recently, we had small spreads of four degrees in 1991 (34/30), six degrees in 1989 (39/33) and seven degrees in 1986 (39/32). The other large spreads were 37 degrees in 2007 (63/26) and 30 degrees in 1981 (60/30).

On the cold side, in 1998 (O'Hare's coldest March 12th) the high was 26 with a low of 10. In 1984 (just half a degree warmer than 1998) the high was 24 with a low of 13. Three years ago, in 2009, the high was 26 with a low of 14. In 1993 the high was 31 with a low of 11. A year earlier, in 1992, the high was 29 with a low of 15. In 2004 the high was 33 with a low of 16. In 1980 the high was 30 with a low of 19. The other cold lows were 15 in 1979 and 16 in 1999. The record low of 1 was set in 1948 at Midway. The record coldest high of 14 occurred way back in 1896, at a time when the official readings were taken adjacent to Lake Michigan. 29 of the last 33 lows (88%) were in the: 10s (a.k.a. teens) (11), 20s (8) and 30s (10). The low in 1960 was 10 which ties 1998 as O'Hare's coldest low of the date. The low in 1969 was 11 which ties 1993 as O'Hare's second coldest low of the date. Our most recent 30s low was 30 in 2001. On the warm side, four lows (12%) were in the: 40s (3) and 50s (1). Besides the warm low of 43 in 1977, the other pre-1979 warm low was 40 in 1966.

There was an instance of back-to-back years in which temperatures were just about as opposite as they can be. In 2009 the high was 26 with a low of 14, overall 16 degrees BELOW normal. Then in 2010 the high was 55 with a low of 40, overall 11.5 degrees ABOVE normal.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:42 and sunrise is at 7:10. Sunset is at 18:57 and twilight ends at 19:25. There's a total of 11 hours, 47 minutes of daylight today and 12 hours, 43 minutes between twilights. We gained two minutes of daylight from yesterday. Tomorrow twilight begins at 6:40 and sunrise is at 7:08. The moon is waning gibbous. Illumination was 80% at midnight, will be 75% at noon and 70% at midnight tonight. Moonset is at 9:25 this morning. Moonrise is at 0:37 tomorrow morning. Moonset is at 10:14 tomorrow morning. Moonlight time is 9 hours, 25 minutes which is nine minutes longer than yesterday.

Spring begins on March 12th (today) and runs for 84 days through June 3rd. Cool Spring begins on March 12th (today) 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 occur infrequently. St. Patrick's Day is in five days.