This report describes the historical weather record at the O'Hare International Airport (Chicago, Illinois, United States) during 1956. This station has records back to December 1947.
Chicago, Illinois has a humid continental climate with hot summers and no dry season. The area within 25 mi of this station is covered by built-up areas (37%), grasslands (36%), oceans and seas (22%), forests (3%), and croplands (3%)
Daylight saving time (DST) was observed at Chicago, Illinois during 1956. There were two time changes during 1956:
1956 was a leap year and thus has 366 days rather than the normal 365. Leap years occur every fourth year and the extra day is always February 29th. In 1956 February 29th falls on a Wednesday.
The summer and winter solstices and the spring and fall equinoxes mark the passing of the seasons. They fall on nearly the same day each year, with differences of a day or two depending on the year. In 1956 they occurred on:
|Spring Equinox||Tuesday, 20 March 1956.|
|Summer Solstice||Thursday, 21 June 1956.|
|Fall Equinox||Sunday, 23 September 1956.|
|Winter Solstice||Friday, 21 December 1956.|
The hottest day of 1956 was July 1, with a high temperature of 102°F. For reference, on that day the average high temperature is 83°F and the high temperature exceeds 91°F only one day in ten. The hottest month of 1956 was June with an average daily high temperature of 84°F.
Relative to the average, the hottest day was April 3. The high temperature that day was 81°F, compared to the average of 53°F, a difference of 28°F. In relative terms the warmest month was October, with an average high temperature of 71°F, compared to an typical value of 62°F.
The longest warm spell was from June 6 to June 25, constituting 20 consecutive days with warmer than average high temperatures. The month of October had the largest fraction of warmer than average days with 84% days with higher than average high temperatures.
The coldest day of 1956 was January 22, with a low temperature of -1°F. For reference, on that day the average low temperature is 16°F and the low temperature drops below -1°F only one day in ten. The coldest month of 1956 was February with an average daily low temperature of 21°F.
Relative to the average, the coldest day was September 20. The low temperature that day was 32°F, compared to the average of 53°F, a difference of 21°F. In relative terms the coldest month was September, with an average low temperature of 51°F, compared to an typical value of 55°F.
The longest cold spell was from March 11 to March 22, constituting 12 consecutive days with cooler than average low temperatures. The month of April had the largest fraction of cooler than average days with 70% days with lower than average low temperatures.
The longest freezing spell was from January 20 to January 26, constituting 7 consecutive days with temperatures strictly below freezing.
The clearest month of 1956 was June, with 60% of days being more clear than cloudy. The longest spell of clear weather was from October 1 to October 11, constituting 11 consecutive days that were clearer than they were cloudy.
The cloudiest month of 1956 was December, with 52% of days being more cloudy than clear. The longest spell of cloudy weather was from December 20 to December 27, constituting 8 consecutive days that were cloudier than they were clear.
This station provides hourly reports of significant weather events at and around the station, but does not report the quantity of precipitation at the station itself. This is common for weather stations located outside of the United States, and for a small subset of stations in the United States that are located at lesser used and smaller airports.
This station reports when significant weather events (including precipitation) are visually observed at or near the station. Such events do not always correspond to measured quantities of liquid equivalent precipitation, such as when the event is near by not at the station, or in the case of solid precipitation that does not melt in the collection basin.
The day in 1956 with the most precipitation observations was December 8. There were 22 hourly weather reports that day (out of a maximum of 24) in which some form of precipitation was observated at or near the station. The month with the most precipitation observations was December, with 168 hourly present weather reports involving some form of precipitation.
As determined by the present weather reports, the longest dry spell was from June 2 to June 15, constituting 14 consecutive days with no observed precipitation. The month with the largest fraction of days without observed precipitation was October, with 84% of days reporting no observed precipitation at all.
The month with the largest fraction of days with at least some observed precipitation was March, with 71% of days reporting some observed precipitation.
In this section we consider only those weather reports that indicate liquid precipitation. For the purposes of this analysis, we include thunderstorms even though some thunderstorms are not accompanied by liquid precipitation.
The month of 1956 with the largest number of those reports was December, with a total of 77 reports. The day with the largest number of those reports was December 6, with a total of 19 reports.
This station reports when snow is observed falling but does not report the quantity of snow that has fallen or the depth of snow on the ground.
In this section we consider hourly weather reports that contain an observation of falling snow. These reports do not necessarily correspond to accumulation.
The first reported snow fall in 1956 was on November 7; the last was on April 17. The month of 1956 with the largest number of those reports was December, with a total of 91 reports. The day with the largest number of those reports was December 8, with a total of 22 reports.
Humidity is an important factor in determining how weather conditions feel to a person experiencing them. Hot and humid days feel even hotter than hot and dry days because the high level of water content in humid air discourages the evaporation of sweat from a person's skin.
When reading the graph below, keep in mind that the hottest part of the day tends to be the least humid, so the daily low (brown) traces are more relevant for understanding daytime comfort than the daily high (blue) traces, which typically occur during the night. Applying that observation, the least humid month of 1956 was September with an average daily low humidity of 37%, and the most humid month was February with an average daily low humidity of 60%.
But it is important to keep in mind that humidity does not tell the whole picture and the dew point is often a better measure of how comfortable a person will find a given set of weather conditions. Please see the next section for continued discussion of this point.
Dew point is the temperature below which water vapor will condense into liquid water. It is therefore also related to the rate of evaporation of liquid water. Since the evaporation of sweat is an important cooling mechanism for the human body, the dew point is an important measurement for understanding how dry, comfortable, or humid a given set of weather conditions will feel.
Generally speaking, dew points below 50°F will feel a bit dry to some people, but comfortable to people accustomed to dry conditions; dew points from 50°F to 68°F are fairly comfortable to most people, and dew points above 68°F are increasingly uncomfortable, becoming oppressive around 77°F.
To take some examples, and basing our categorization on the daily high dew point in 1956, January had 31 dry days, no comfortable days, and no humid days; April had 26 dry days, 4 comfortable days, and no humid days; July had no dry days, 21 comfortable days, and 10 humid days; and October had 13 dry days, 18 comfortable days, and no humid days.
The highest sustained wind speed was 55 mph, occurring on March 11; the highest daily mean wind speed was 30 mph (November 21);
The windiest month was November, with an average wind speed of 13 mph. The least windy month was February, with an average wind speed of 9 mph.
Visibility is the maximum distance at which a given reference object or light can be clearly discerned. In the United States, visibilities that are greater than or equal to 10 miles are typically reported as 10 miles.
The day of 1956 with the lowest average visibility was November 2, with an average visibility of 0.6 mi. The month with the lowest average visibility was February, with an average visibility of 7.1 mi. With an average visibility of 11.1 mi, the month of September had the highest average visibility.
The cloud ceiling is the altitude of the lowest layer of clouds that are at categorized as broken (mostly cloudy) or overcast (cloudy). If no such cloud layer exists then the ceiling is unlimited and no value is reported.
The day of 1956 with the lowest average cloud ceiling was September 26, with an average cloud ceiling of 49'. The month with the lowest average cloud ceiling was February, with an average cloud ceiling of 4262'. The month of October has the highest average cloud ceiling, with an average cloud ceiling of 24714'.