December 21: ORD

Today is December 21st. It's the 356th day of the year. Ten days remain. It's week 51 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. Observations have been official at O'Hare since Thursday, January 17, 1980.

According to the National Climatic Data Center (NCDC), the normal high is 33 and the normal low is 19. The 30-year averages are 34 and 18.

On the warmer side, two years ago the high was 50 with a low of 38. In 1984 the high was 56 with a low of 30. A decade later, in 1994, the high was 51 with a low of 30. In 1979 the high was 48 with a low of 28. Other warm highs were 47 in 2003, 45 in 1990 and 44 in 1986. Another warmer low was 33 last year. The record high of 62 occurred in 1967. The record warmest low of 49 was set back in 1918. 14 of the last 30 highs were 30s. On the warmer side, eight highs were in the 40s (5) and 50s (3). On the colder side, eight highs were in the 0s (1), 10s (3) and 20s (4).

In looking back through the years to the first December at O'Hare in 1958, the following instances were notable. In 1972 the high was 35 with a low of 33, a two degree spread. In 1967 the high was 61 (record high of 62 at Midway) with a low of 19, a 42 degree spread (and bonus 60s day). In 1965 the high was 35 with a low of 29, a six degree spread. In 1964 the high was 40 with a low of 10, a 30 degree spread. In 1963 the high was 13 with a low of -11, a cold day. In 1962 the high was 30 with a low of 24, a six degree spread. In 1960 the high was 9 with a low of -7, a cold day.

More recently, we had small spreads of five degrees in 1993 (29/24), five degrees last year (38/33), six degrees in 2002 (24/28) and seven degrees in 1983 (23/16).

On the cold side, in 1989 the high was the record coldest high of 0 with the record low of -14. In 2000 the high was 19 with a low of -7. A year earlier, in 1999, the high was 14 with a low of 1. In 1985 the high was 18 with a low of -2. Two decades later, in 2005, the high was 20 with a low of 3. In 1980 the high was 21 with a low of 5. 20 of the last 30 lows were 10s (8) and 20s (12). On the warmer side, four lows were 30s. On the colder side, six lows were negative 10s (1), negative zeros (2) and zeros (3).

It is very cold today. At O'Hare, the temperature dropped 13 degrees from midnight to 2 AM (14 to 1). At 10 AM O'Hare is still experiencing the bottom as it is -6 with a wind chill of -32 as the winds are west at 26 mph, gusting to 41. At Midway, the temperature dropped 16 degrees from 11 PM to 2 AM (21 to 5). At 10 AM Midway is still experiencing the bottom as it is -5 there with a wind chill of -32 as the winds are west at 28, gusting to 37. In West Chicago, the drop was 11 degrees from 11 PM to 1 AM (14 to 3). Their bottom was at 8 AM when it was -6. At 10 AM it's -4 with a wind chill of -29 as winds are west/southwest at 26, gusting to 35. Rockford experienced a drop of 18 degrees from 9 PM to midnight (21 to 3). Their bottom was at 8 AM when it was -8. At 10 AM it's -5 with a wind chill of -29 as winds are west at 23, gusting to 37. The predicted high for today is between 1 and 5 above zero.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:47 and sunrise is at 7:19. Sunset is at 16:24 and twilight ends at 16:56. There's a total of 9 hours, 5 minutes of daylight today and 10 hours, 9 minutes between twilights. Tomorrow twilight begins at 6:48 and sunrise is at 7:19. The moon is waning crescent. Illumination was 32% at midnight, will be 28% at noon and 23% at midnight tonight. Moonrise was at 1:55 and moonset is at 12:27. Moonrise is at 3:00 tomorrow. Moonlight time is 10 hours, 32 minutes today. The Winter Solstice is today at 6:04.

Today is a major snow day in O'Hare's history. In 1969, 0.3 inches fell. This was the first of four days of measurable snowfall, part of a total of 13.5 inches during the period.

Christmas Eve is in three days and Christmas Day is in four days. New Year's Eve is in ten days and New Year's Day is in 11 days. -Bernie-