May 14: ORD

Today is May 14th. It's the 135th day of the year. 231 days remain. It's week 20 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. From Friday, January 1, 1926 through Tuesday, June 30, 1942, the official site was at the University of Chicago. 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 69 and the normal low is 48. I've calculated the 33-year averages at 68 and 47.

On the warm side, in 1982 (O'Hare's second warmest May 14th) the high was the record high of 92 with a low of 60, a 32 degree spread. In 1991 the high was 87 with a low of 60. In 2007 the high was 90 with a low of 56, a 34 degree spread. The other warm highs were 86 in 1985, 84 in 1987, 84 in 1998 and 81 in 1988. The record warmest low of 68 was set in 1962 at Midway. 16 of the past 33 highs (49%) were in the 60s. On the warm side, ten highs (30%) were in the: 70s (2), 80s (6) and 90s (2). The 70s highs, post 1978, occurred in the back-to-back years of 1994 and 1995. Both highs were right at 70 degrees! Our most recent 80s high was 84 in 1998. On the cold side, seven highs (21%) were in the 50s. O'Hare's warmest May 14th was in 1962 as the high was 86 with a low of 67 (O'Hare's warmest low of the date).

In looking back through the years to the first May at O'Hare in 1959, the following instances were notable: In 1978 the high was a cold 48 with a low of 44, a four degree spread and cold day. In 1977 the high was a warm 82 degrees. In 1973 the high was 53 with a low of 34, a cold day. In 1970 the high was a cool 57 degrees. In 1968 the low was a warm 61 degrees. In 1965 the high was a warm 84 with a low of 46, a 38 degree spread. In 1964 the high was 68 with a cold low of 36, a 32 degree spread. In 1962 the high was 86 with a low of 67, a hot day and year of the record warmest low. In 1961 the high was 83 with a low of 60, a warm day. In 1960 the high was 77 with a low of 43, a 34 degree spread. In 1959 the high was a cool 53 with a low of 42, a cool day.

More recently, we had additional large spreads of 42 degrees in 1988 (81/39), 37 degrees in 1993 (80/43), 33 degrees in 1984 (69/36), 32 degrees in 1998 (84/52), 32 degrees in 1985 (86/54) and 30 degrees in 1987 (84/54).
 
On the cool side, in 1981 the high was 50 with a low of 45, a five degree spread. In 1996 the high was 57 with a low of 38. The other cold low was 36 in 1984. The other cool highs were 53 last year, in 2011, 55 in 1997 and 56 in 2006. The record low of 32 and record coldest high of 40 were set on the same cold day way back in 1895, at a time when the official readings were taken adjacent to Lake Michigan. 20 of the last 33 lows (61%) were in the 40s. O'Hare recorded eight consecutive 40s lows from 1999 through 2006. Three lows (9%) were in the cold 30s. Ten lows (30%) were in the warm: 50s (8) and 60s (2). O'Hare's coldest May 14th was in 1973 as the high was 53 with a low of 34 (O'Hare's coldest low of the date). O'Hare's second coldest May 14th was in 1978 as the high was 48 (O'Hare's coldest high of the date) with a low of 44.

There was an instance of back-to-back years in which temperatures were just about as opposite as they can be. In 1981 the high was 50 with a low of 45,  overall 11.5 degrees BELOW normal. Then in 1982 the high was 92 with a low of 60, overall 17 degrees ABOVE normal.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:01 and sunrise is at 5:33. Sunset is at 20:07 and twilight ends at 20:39. There's a total of 14 hours, 34 minutes of daylight today and 15 hours, 38 minutes between twilights. We gained two minutes of daylight from yesterday. Tomorrow twilight begins at 5:00 and sunrise is at 5:32. The moon is waning crescent, having reached last quarter two days ago at 16:47. Illumination was 37% at midnight, will be 32% at noon and 27% at midnight tonight. Moonrise was at 2:14 this morning. Moonset is at 14:22 this afternoon. Moonrise is at 2:39 tomorrow morning. Moonlight time is 12 hours, 8 minutes which is 35 minutes longer than yesterday. 

Spring began on March 12th and runs for 84 days through June 3rd. Warm Spring began on April 13th and runs for 52 days through June 3rd. High temperatures in this period are usually in the 50s, 60s and 70s. Highs in the 80s and 90s occur infrequently. Armed Forces Day is in five days. National Maritime Day is in eight days.