May 29: ORD

Today is May 29th. It's the 149th day of the year. 216 days remain. It's week 22 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 75 and the normal low is 52. I've calculated the 32-year averages at 75 and 53.

On the warm side, in 2006 the high was 91 with a low of 68. In 1991 the high was 87 with the record warmest low of 71. The former record warmest low was 70 in 1962. In 1987 the high was 89 with a low of 66. In 1999 the high was 86 with a low of 65. Other hot 80s highs were 89 in 1988 and 88 in 2007. The record high of 95 was set back in 1942. Another warm low was 64 in 1998. 30 of the past 32 highs (94%) were in the: 60s (11), 70s (7) and 80s (12). One high was in the cool 50s and one high was in the warmer 90s.

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 hot 88 with a low of 63, a hot day. In 1977 the high was 89 with a low of 64, a hot day. In 1973 the high was a cool 55 with a low of 46, a cool day. In 1972 the low was a warm 64 degrees. In 1971 the high was 75 with a low of 41, a 34 degree spread. In 1970 the high was 85 with a warm low of 67, a warm day. In 1967 the high was a cool 62 degrees. In 1966 the high was 62 with a low of 35, a cool day. In 1965 the high was 55 with a low of 32, a cold day. In 1964 the high was 60 with a low of 36, a cool day. In 1962 the high was 87 with a low of 68, a hot day. 1962 was the year of the record warmest low. In 1961 the high was 62 with a low of 40, a cool day.

More recently, there was a small spread of seven degrees in 1997 (62/55). There were large spreads of 37 degrees in 1979 (82/45), 33 degrees in 1992 (72/39), 31 degrees in 1985 (75/44) and 30 degrees in 1988 (89/59).

On the cool side, in 1984 we had the only 50s high of 57 with the record-tying low of 37. The record low of 37 was originally set in 1965. In 1996 the high was 60 with a low of 40. Three years earlier, in 1993, the high was 61 with a low of 41. Other cool highs were 62 in 1997, 62 in 2001 and 63 in 1990. Another cool low was 39 in 1992. The record coolest high of 46 occurred way back in 1889. 29 of the last 32 lows (91%) were in the: 40s (12), 50s (9) and 60s (8). Two lows were in the cold 30s and one was in the warmer 70s.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 4:48 and sunrise is at 5:21. Sunset is at 20:21 and twilight ends at 20:54. There's a total of 15 hours of daylight today and 16 hours, 6 minutes between twilights. We gained two minutes of daylight from yesterday. Tomorrow twilight begins at 4:47 and sunrise is at 5:21. The moon is waning crescent. Illumination was 12% at midnight, will be 9% at noon and 7% at midnight tonight. Moonrise is at 3:09 this morning. Moonset is at 17:33 this afternoon. Moonrise is at 3:39 tomorrow morning. Moonlight time is 14 hours, 24 minutes which is 34 minutes longer 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. Memorial Day is tomorrow. Flag Day is in 16 days.