May 30: ORD

Today is May 30th. It's the 150th day of the year. 215 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 78 and 55.

On the hot side, in 2006 the high was 89 degrees with a low of 67. In 1991 the high was 88 with a low of 66. Three years later, in 1994, the high was 90 with a low of 64. In 1987 the high was 85 with a low of 68. Two decades later, in 2007, the high was 87 with a low of 66. In 1980 the high was 86 with a low of 66. Three decades later (last year, 2010), the high was 91 with a low of 61, a 30 degree spread. In 1988 the high was 91 with a low of 60, a 31 degree spread. The other warm 80s high was 87 in 1998. The other warm lows were 64 in both 1985 and 2002. The record high of 93 was set in 1942 and tied in 1953. The record warmest low of 72 occurred back in 1921. 28 of the past 32 highs (88%) were in the: 60s (7), 70s (8) and 80s (13). Our most recent 60s high was 60 a decade ago in 2001. Three highs were in the hot 90s. One high was in the cool 50s (55 in 1983). The high today is predicted to be at least 90. This would be the fourth 90s high for May 30th in the history of O'Hare. Some meteorologists are predicting a new record high.

In looking back through the years to the first May at O'Hare in 1959, the following instances were notable: In 1971 the high was 82 with a low of 45, a 37 degree spread. In 1970 the low was a warm 68 degrees. In 1967 the high was a cool 63 degrees. In 1964 the high was 69 with a cold low of 34, a 35 degree spread and cool day. In 1963 the high was 74 with a low of 41, a 33 degree spread. In 1962 the low was a warm 67 degrees. In 1961 the high was 76 with a cold low of 37, a 39 degree spread.

More recently, there were large spreads of 31 degrees in 1984 (70/39) and 31 degrees in 2000 (80/49).

On the cool side, in 1983 the high was the only 50s high for the date at 55 degrees with a low of 45. In 1996 the high was 65 with a low of 36. Five years later, in 2001, the high was 60 with a low of 45. Another cool low was 39 in 1984. Both records were set way back in the 19th century. The record low of 35 was set way back in 1873. The record coolest high of 42 occurred way back in 1889. 30 of the last 32 lows (94%) were in the: 40s (9), 50s (9) and 60s (12). Two lows were in the cold 30s.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 4:47 and sunrise is at 5:21. Sunset is at 20:21 and twilight ends at 20:55. There's a total of 15 hours of daylight today and 16 hours, 8 minutes between twilights. We gained no minutes of daylight from yesterday. Tomorrow twilight begins at 4:46 and sunrise is at 5:20. The moon is waning crescent and will be new in two days at 16:03. Illumination was 7% at midnight, will be 5% at noon and 3% at midnight tonight. Moonrise is at 3:39 this morning. Moonset is at 18:34 this afternoon. Moonrise is at 4:15 tomorrow morning. Moonlight time is 14 hours, 55 minutes which is 31 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 today. Flag Day is in 15 days.