March 17: ORD

Today is March 17th. It's the 76th day of the year. 289 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.

According to the National Climatic Data Center (NCDC), the normal high is 47 and the normal low is 29. I've calculated the 32-year averages at 44 and 29.

On the warm side, two years ago, in 2009, the high was a record-tying 74 with a low of 41, a 33-degree spread. In 2003 the high was 73 with a low of 40, also a 33 degree spread. In 1999 the high was 59 with a low of 41. The co-record high of 74 and record warmest low of 49 were set on the same day way back in 1894. Another warm high was 63 last year, the first 60s high of the last 32 years. 25 of the last 32 highs (78%) were in the: 30s (14) and 40s (11). Our most recent 40s high was 41 in 2002. On the warmer side, six highs were in the: 50s (3), 60s (1) and 70s (2). On the colder side, one high was in the 20s. Today is the mode (most frequent) date for our first high in the 70s based upon the past 32 years.

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 a cold 34 with a low of 19, a cold day. In 1969 the high was a warm 69 with a low of 36, a 33 degree spread and warm day. In 1968 the high was a warm 66 with a low of 26, a 40 degree spread. In 1967 the high was 25 with a low of 11, a cold day. In 1966 the high was 76 with a low of 43, a 33 degree spread and warm day. And although this high of 76 beats the record of 74, O'Hare was not the official station of record in 1966. In 1964 the high was 31 with a low of 14, a cold day. In 1961 the high was a cold 34 degrees. In 1960 the high was a cold 30 with a low of 23, a seven degree spread and cold day. In 1959 the high was 27 with a low of 15, another cold day.

March 17, 1966 was quite a day. The following are highs and lows at various stations: Springfield: 73/53, Wheaton College: 72/43, DeKalb: 71/43, Marengo: 73/40, Rockford: 73/41, Barrington: 74/44, University of Chicago: 73/45, Chicago in Grant Park near Buckingham Fountain: 73/44, Midway: 73/40. Midway had jumps of five degrees in the back to back hours of 9-10 AM (57 to 62) and 10-11 AM (62 to 67). It's unusual that O'Hare's temperature was higher than Midway's. Perhaps there was a wind component off the lake which held Midway's reading down a bit.

Likewise, it was pleasantly warm two years ago in 2009. Not only was it O'Hare's warmest March 17 of the past 32 years (and tied the record high), other locations around the area felt the warmth. The high and low were 75 and 40 at Rockford. Highs were 74 at Midway, 72 at Barrington, 73 at: DeKalb, Elgin, Northerly Island, McHenry, National Weather Service/Romeoville, 75 at the Chicago Botanical Garden and 78 at Streamwood.

More recently, we had small spreads of five degrees in 1984 (32/27), six degrees in: 1989 (35/29), 1998 (39/33), 2005 (35/29) and seven degrees in 2002 (41/34). There was a large spread of 31 degrees last year (in 2010) (63/32).

On the cold side, in 1993 the high was 29 with a low of 12. In 1981 the high was 38 with a low of 18. Other cold highs were 32 in 1984 and 35 in three years: 1989, 1996 and 2005. The record low of -1 was set way back in 1900. The record coldest high of 11 occurred back in 1941. 26 of the last 32 lows (81%) were in the: 20s (13) and 30s (13). Three lows were in the cold 10s (a.k.a. teens). Three lows were in the warmer 40s.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:34 and sunrise is at 7:02. Sunset is at 19:02 and twilight ends at 19:30. There's a total of 12 hours of daylight today and 12 hours, 56 minutes between twilights. We gained three minutes of daylight from yesterday. Tomorrow twilight begins at 6:33 and sunrise is at 7:01. The moon is waxing gibbous and will be full in two days. Illumination was 91% at midnight, will be 94% at noon and 96% at midnight tonight. Moonset is at 5:28 this morning. Moonrise is at 16:52 this afternoon. Moonset is at 5:59 tomorrow morning. Moonlight time is 12 hours, 36 minutes which is 43 minutes shorter than yesterday.

St. Patrick's Day is today. The warm part of Spring (Warm Spring) begins in 27 days on April 13. Warm Spring runs for 52 days, through June 3. High temperatures in this period are usually in the 50s, 60s and 70s. Warmer 80s and 90s occur infrequently. -Bernie-