March 11: ORD

Today is March 11th. It's the 71st day of the year. 295 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 43 and 25.

On the warm side, in 1990 (O'Hare's second warmest March 11th) the high was the record high of 74 with a low of 42, a 32 degree spread. In 2006 the high was 67 with a low of 43. Two years ago, in 2010, the high was 60 with a low of 44. In 1995 the high was 62 with a low of 40. The other warm highs were 60 in 1988 and 59 a year later in 1989. The record warmest low of 55 occurred way back in 1902, at a time when the official readings were taken adjacent to lake Michigan. 21 of the past 33 highs (64%) were in the: 30s (10) and 40s (11). On the warm side, eight highs (24%) were in the: 50s (3), 60s (4) and 70s (1). O'Hare's warmest March 11th was in 1977 when the high was 68 along with a low of 50. The other pre-1979 warm highs were 70 in 1972, 65 in 1973 and 57 in 1966. On the cold side, four highs (12%) were in the 20s. The pre-1979 cold high was 25 in 1960.

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 39 with a low of 33, a six degree spread. In 1977 the high was 68 with a low of 50, a warm day. In 1975 the high was 35 with a low of 28, a seven degree spread. In 1974 the high was 41 with a low of 36, a five degree spread. In 1973 the high was 65 with a low of 44, a warm day. In 1972 the high was a warm 70 with a low of 33, a spread of 37 degrees and a warm day. In 1969 the high was 31 with a low of 11, a cold day. In 1967 the high was 39 with a low of 33, a six degree spread. In 1966 the high was 57 with a low of 46, a warm day. In 1965 the high was a cold 32 degrees. In 1963 the high was 36 with a low of 29, a seven degree spread. In 1962 the high was 39 with a low of 32, a seven degree spread. In 1960 the high was a cold 25 with a low of 20, a five degree spread and cold day.

More recently, we had no other small or large spreads.

On the cold side, in 1979 (O'Hare's coldest March 11th) the high was 27 with a low of 4 (O'Hare's coldest temperature of the date). In 1998 the high was 22 (O'Hare's coldest high of the date and our most recent 20s high) with a low of 13. In 1984 the high was 25 with a low of 12. In 1992 the high was 29 with a low of 11. In 1980 the high was 31 with a low of 13. The other cold highs were 31 in 1993 and 33 three years ago in 2009. The record low of 3 was set in 1979 at Midway. The record coldest high of 20 occurred in 1948 at Midway. 16 of the last 33 lows (49%) were in the 20s. On the cold side, eight lows (24%) were in the: single digits (1) and 10s (a.k.a. teens) (7). Prior to 1979, the coldest low was 11 in 1969. On the warm side, nine lows (27%) were in the: 30s (5) and 40s (4). Prior to 1979, the warm lows were 46 in 1966 and 44 in 1973.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:43 and sunrise is at 7:11. Sunset is at 18:56 and twilight ends at 19:24. There's a total of 11 hours, 45 minutes of daylight today and 12 hours, 41 minutes between twilights. We gained three minutes of daylight from yesterday. Tomorrow twilight begins at 6:42 and sunrise is at 7:10. The moon is waning gibbous, having reached the full Worm (a.k.a. Sap) moon three days ago at 3:39. Illumination was 89% at midnight, will be 85% at noon and 80% at midnight tonight. Moonset is at 8:42 this morning. Moonrise is at 23:26 tonight. Moonset is at 9:25 tomorrow morning. Moonlight time is 9 hours, 16 minutes which is 36 minutes shorter than yesterday. Moonlight time is at its least today.

Winter began December 1st and runs for 102 days through March 11th (today). High temperatures in this period are usually in the 20s and 30s. Highs in the 40s and 50s occur infrequently. St. Patrick's Day is in six days.