May 15: ORD

Today is May 15th. It's the 135th day of the year. 230 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.

According to the National Climatic Data Center (NCDC), the normal high is 69 and the normal low is 47. I've calculated the 32-year averages at 68 and 48.

On the warm side, in 1998 the high was 86 with a low of 64. In 1991 the high was 87 with a low of 57, a 30 degree spread. In 1988 the high was 80 with a low of 63. In 2001 the high was 88 with a low of 55, a 33 degree spread. In 1982 the high was 85 with a low of 56. The record high of 91 and record warmest low of 71 were set on the same day in 1962. 19 of the last 32 highs (59%) were in the: 60s (11) and 70s (8). Our most recent 70s high was 75 in 2002. Six highs (19%) were in the 80s. Our most recent 80s high was 80 in 2007. Seven highs (22%) were in the 50s.

In looking back through the years to the first May at O'Hare in 1959, the following instances were notable: In 1977 the high was a warm 82 degrees. In 1971 the high was a warm 83 with a low of 58, a warm day. In 1968 the high was 82 with a low of 60, a warm day. In 1967 the high was a cool 56 degrees. In 1965 the high was 81 with a low of 60, a warm day. In 1964 the high was a warm 81 with a low of 45, a 36 degree spread. In 1963 the high was a cool 55 degrees. In 1962 the high was 89 with a low of 71, a hot day. 1962 was also the year of the record high and record warmest low. In 1960 the high was a warm 82 degrees. In 1959 the high was a cool 55 degrees.

More recently, we had large spreads of 35 degrees in 1992 (77/42) and 35 degrees in 2002 (75/40).

On the cool side, in 1997 the high was 51 with a low of 38. In 1983 the high was 53 with a low of 37. The other cool highs were 54 in 2005, 55 in 2004, 57 in 2003 and 57 three years ago (in 2008). The other 30s lows were 38 in 1984 and 39 in 2004. The record low of 35 was set way back in 1895. The record coolest high of 44 occurred back in 1904. 18 of the last 32 lows (56%) were in the 40s. Four lows (13%) were in the cold 30s. Ten lows (31%) were in the warmer: 50s (8) and 60s (2).

The past few days have been wild this year and in some cases greatly contrasted with last year. May 10 (Tue.): in 2010, was tied with another year as fourth coldest; this year it was the second warmest with a high of 90 and low of 62, 20 degrees above normal. The high of 90 was a new record, breaking 89 in 1896 (115 years ago). The warmest for May 10 at O'Hare remains 1979 with a high of 90 and low of 67, +22.5 of normal. This high of 90 did not become the record since O'Hare was not the official station of record in 1979. May 11 (Wed.): in 2010, was tied with another year as third coldest; this year it was the warmest with a high of 87 and low of 63, 18 degrees above normal. It beat 1982's record high of 89 and low of 58 (+16.5 of normal) & 1985's high of 87 and low of 60 (also +16.5 of normal). May 12 (Thu.): in 2010, was tied with three other years as the fourth coldest; this year it was the fourth warmest with a high of 86 and low of 58, 15 degrees above normal. 2004 remains the warmest (85/66, +18.5 of normal). 1991 remains second warmest (84/63, +16.5 of normal). 2000 remains third warmest (85/60, +15.5 of normal). May 13 (Fri.): sixth warmest this year with a high of 77 and low of 47, finally cooling off late in the day. May 14 (Sat.): high of 53, low of 45, nine below normal; tied 2006 (56/42) as third coldest. The coldest days were 10.5 below normal: 1981 (50/45) and 1996 (57/38). May 15 (Sun.): IF high and low are 50 & 40, it will be the second or third coldest May 15.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight is at 5:00 and sunrise is at 5:32. Sunset is at 20:07 and twilight ends at 20:40. There's a total of 14 hours, 35 minutes of daylight today and 15 hours, 40 minutes between twilights. We gained three minutes of daylight from yesterday. Tomorrow twilight begins at 4:59 and sunrise is at 5:31. The moon is waxing gibbous and will be full as the full Flower moon in two days at 6:09. Illumination was 93% at midnight, will be 96% at noon and 98% at midnight tonight. Moonset is at 3:57 this morning. Moonrise is at 18:27 tonight. Moonset is at 4:35 tomorrow morning. Moonlight time is 9 hours, 30 minutes which is 43 minutes shorter than yesterday.

The warm part of Spring (Warm Spring) began 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. Armed Forces Day is in six days. National Maritime Day is in seven days. Memorial Day is in 15 days. -Bernie-