May 16: ORD

Today is May 16th. It's the 136th day of the year. 229 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 70 and the normal low is 47. I've calculated the 32-year averages at 71 and 48.

On the warm side, in 2001 the high was 89 with a low of 64. A decade earlier, in 1991, the high was 86 with a low of 63. The next year, 1992, the high was 88 with a low of 58, a 30 degree spread. In 1998 the high was 82 with a low of 62. In 1986 the high was 79 with a low of 62. Other mid 80s highs were all 83 degrees: in 1982, 1987 and 1999. Other warm lows were 60 in 1990 and 59 in 1995. The record high of 94 and record warmest low of 69 were set on the same day in 1962. 16 of the highs over the last 32 years (50%) were in the 60s. 15 highs (47%) were in the warmer: 70s (8) and 80s (7). One high (3%) was in the cold 50s. Today's high is predicted (by the Weather Channel) to be 56 at O'Hare, so this will likely be only the second high in the 50s in O'Hare's history for May 16 (since 1959). This will break a string of nine consecutive years (2002-2010) in which highs were in the 60s or 70s.

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 86 with a low of 61, a hot day. In 1969 the high was 85 with a low of 60, a very warm day. In 1962 the high was 92 with a low of 69, a hot day. 1962 was also the year of the record high and record warmest low.

More recently, we had a small spread of 6 degrees in 1996 (57/51). The large spreads were: 40 degrees in 1987 (83/43), 35 degrees in 1997 (68/33), 33 degrees in 2004 (70/37), 33 degrees three years ago in 2008 (73/40) and 32 degrees in 1981 (75/43).

On the cool side, the back-to-back years of 1983 and 1984 were the coldest of the past 32 years. In 1983 the high was 63 with a low of 35. In 1984 the high was 64 with a low of 36. In 1996 the high was just 57, O'Hare's only sub-60 degree high for the date. Keep in mind, the predicted high for today is in the 50s as well. The record low of 33 was set in 1997. The former record low of 34 was set way back in 1888. The record coolest high of 44 occurred way back in 1891. 17 of the last 32 lows (53%) were in the 40s. In eight of the last nine years (2002-2010), lows were in the 40s. Four lows (13%) were in the cold 30s. Our most recent 30s low was 37 in 2004. 11 lows (34%) were in the warmer: 50s (6) and 60s (5).

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.): It was the coldest May 15 in O'Hare's history as the high of 46 and low of 41 made the day 14.5 degrees below normal. It beat the prior two coldest days of 1997 (51/38), -13.5 of normal and 1983 (53/37), -13 of normal. The high of 46 is just two degrees above the record coldest high of 44 set way back in 1904. May 16 (Mon.): Today is on course to be the coldest May 16 in the history of O'Hare (going back to 1959). A high in the mid 50s is predicted after a low in the 30s this morning.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight is at 4:59 and sunrise is at 5:31. Sunset is at 20:08 and twilight ends at 20:41. There's a total of 14 hours, 37 minutes of daylight today and 15 hours, 42 minutes between twilights. We gained two minutes of daylight from yesterday. Tomorrow twilight begins at 4:58 and sunrise is at 5:31. The moon is waxing gibbous and will be full as the full Flower moon tomorrow at 6:09. Illumination was 98% at midnight, will be 99% at noon and 100% at midnight tonight. Moonset is at 4:35 this morning. Moonrise is at 19:42 tonight. Moonset is at 5:20 tomorrow morning. Moonlight time is 8 hours, 53 minutes which is 37 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 five days. National Maritime Day is in six days. Memorial Day is in 14 days. -Bernie-