May 18: ORD

Today is May 18th. It's the 138th day of the year. 227 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 49. I've calculated the 32-year averages at 69 and 49.

On the warm side, in 1996 the high was 90 with the record-tying warmest low of 72 (tied with 1911). In 1984 the high was 91 with a low of 61, a 30 degree spread. In 1998 the high was 90 with a low of 62. In 1979 the high was 85 with a low of 60. In 1982 the high was 82 with a low of 61. The record high of 93 was set in 1962. 26 highs over the last 32 years (81%) were in the: 50s (7), 60s (10) and 70s (9). Six highs were in the warmer: 80s (3) and 90s (3).

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 92 with a low of 64, a hot day. In 1975 the high was a hot 86 with a low of 50, a 36 degree spread. In 1974 the high was a cool 58 degrees. In 1972 the high was a warm 85 degrees. In 1971 the high was 85 with a low of 69, a warm day. In 1970 the high was 78 with a low of 45, a 33 degree spread. In 1969 the high was a cold 47 with a low of 45, a two degree spread and cold day. In 1967 the high was a warm 85 with a low of 55, a 30 degree spread. In 1965 the high was a warm 82 with a low of 46, a 36 degree spread. In 1964 the high was a hot 89 with a low of 56, a 33 degree spread and warm day. In 1962 the high was 91 with a low of 71, a hot day and year of the record high of 93 at Midway. In 1961 the high was a cool 55 with a low of 41, a cool day.

More recently, we had large spreads of 36 degrees in 1997 (77/41), 33 degrees in 1993 (70/37), 30 degrees in 1987 (81/51) and 30 degrees in 1988 (70/40).

On the cool side, in 2002 the high was 54 with the record low of 34 degrees (broke the former record of 35 set way back in 1894). Three years ago, in 2008, the high was 55 with a low of 44. In 1991 the high was 54 with a low of 45. Other cool highs were 55 in 1986, 57 in 1981 and 58 in 1995. Another cold low was 37 in 1993. The record coolest high of 45 occurred way back in 1900. 18 of the last 32 lows (56%) were in the 40s. Three lows (9%) were in the cold 30s. 11 lows (34%) were in the warmer: 50s (6), 60s (4) and 70s (1).

The past few days have been wildly cool this year. 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.): It was the coldest May 16 in O'Hare's history as the high of 52 and low of 37 made the day 14.5 degrees below normal. It beat the prior coldest day of 1983 (63/35), -10 of normal. The high of 52 was cooler than our other 50s high of 57 in 1996. May 17 (Tue): It was the fifth coldest May 17 of the last 33 years with a high of 60 and low of 40. May 18 (Wed): Today is on course to be one of the coldest May 18ths in the history of O'Hare (going back to 1959). A high in the mid 50s is predicted.

The following is courtesy of Tom Skilling/Chicago Weather Center Blog:
Mid-May high temperatures the coolest here in 66 years; area moves into a fifth below normal day
Chicago's high temperatures between May 14 and 17 have been the chilliest observed at O'Hare since official observations began at the Northwest side site in 1959. Expanding the comparison of these highs to the entire 141-year meteorological record for the city reveals a chillier mid-May period hasn't occurred in the 66 years since 1945.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 4:57 and sunrise is at 5:30. Sunset is at 20:10 and twilight ends at 20:43. There's a total of 14 hours, 40 minutes of daylight today and 15 hours, 46 minutes between twilights. We gained two minutes of daylight from yesterday. Tomorrow twilight begins at 4:56 and sunrise is at 5:29. The moon is waning gibbous, having passed the full Flower moon yesterday at 6:09. Illumination was 99% at midnight, will be 98% at noon and 96% at midnight tonight. Moonset is at 6:13 this morning. Moonrise is at 21:57 tonight. Moonset is at 7:13 tomorrow morning. Moonlight time is 8 hours, 16 minutes which is 10 minutes shorter than yesterday and is at it's shortest for the next several days.

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 three days. National Maritime Day is in four days. Memorial Day is in 12 days. -Bernie-