This report describes the historical weather record at the Central Illinois Regional Airport (Bloomington, Illinois, United States) during 2012. This station has records back to April 1976.
Bloomington, Illinois has a humid continental climate with hot summers and no dry season. The area within 25 mi of this station is covered by croplands (98%)
Daylight saving time (DST) was observed at Bloomington, Illinois during 2012. There were two time changes during 2012:
2012 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 2012 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 2012 they occurred on:
|Spring Equinox||Tuesday, 20 March 2012.|
|Summer Solstice||Wednesday, 20 June 2012.|
|Fall Equinox||Saturday, 22 September 2012.|
|Winter Solstice||Friday, 21 December 2012.|
The hottest day of 2012 was July 6, with a high temperature of 102°F. For reference, on that day the average high temperature is 84°F and the high temperature exceeds 91°F only one day in ten. The hottest month of 2012 was July with an average daily high temperature of 92°F.
Relative to the average, the hottest day was March 15. The high temperature that day was 81°F, compared to the average of 49°F, a difference of 32°F. In relative terms the warmest month was March, with an average high temperature of 65°F, compared to an typical value of 49°F.
The longest warm spell was from June 27 to July 28, constituting 32 consecutive days with warmer than average high temperatures. The month of July had the largest fraction of warmer than average days with 97% days with higher than average high temperatures.
The coldest day of 2012 was January 14, with a low temperature of 3°F. For reference, on that day the average low temperature is 20°F and the low temperature drops below 3°F only one day in ten. The coldest month of 2012 was January with an average daily low temperature of 21°F.
Relative to the average, the coldest day was October 8. The low temperature that day was 30°F, compared to the average of 47°F, a difference of 17°F. In relative terms the coldest month was November, with an average low temperature of 31°F, compared to an typical value of 34°F.
The longest cold spell was from September 7 to September 25, constituting 19 consecutive days with cooler than average low temperatures. The month of September had the largest fraction of cooler than average days with 73% days with lower than average low temperatures.
The clearest month of 2012 was July, with 97% of days being more clear than cloudy. The longest spell of clear weather was from June 25 to July 20, constituting 26 consecutive days that were clearer than they were cloudy.
The cloudiest month of 2012 was December, with 61% of days being more cloudy than clear. The longest spell of cloudy weather was from December 15 to December 21, constituting 7 consecutive days that were cloudier than they were clear.
This station reports both the quantity of liquid precipitation and categorical observations of precipitation (e.g., moderate rain, or heavy snow). Both are subject to erroneous reports, but the former is particularly prone to false reports, especially ones indicating an excessive quantity of precipitation. Please bear this in mind when reading the extrema reported in this section.
The day with the largest quantity of precipitation was September 1. That day saw 4.134" of liquid (or liquid equivalent) precipitation, compared to a median value of 0.178". The month with the most precipitation was September, with 6.634", compared to a median value of 3.018".
As determined by quantitative measurements, the longest dry spell was from January 2 to January 17, constituting 16 consecutive days with no measured precipitation. The month with the largest fraction of dry days was July, with 94% of days reporting no measured precipitation at all.
The month with the largest fraction of days with at least some measured precipitation was October, with 42% of days reporting some measured precipitation.
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 2012 with the most precipitation observations was January 12. There were 16 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 January, with 78 hourly present weather reports involving some form of precipitation.
As determined by the present weather reports, the longest dry spell was from June 5 to June 16, constituting 12 consecutive days with no observed precipitation. The month with the largest fraction of days without observed precipitation was July, with 87% of days reporting no observed precipitation at all.
The month with the largest fraction of days with at least some observed precipitation was January, with 42% 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 2012 with the largest number of those reports was October, with a total of 56 reports. The day with the largest number of those reports was August 26, with a total of 12 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 2012 was on December 17; the last was on March 4. The month of 2012 with the largest number of those reports was January, with a total of 65 reports. The day with the largest number of those reports was January 12, with a total of 16 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 2012 was June with an average daily low humidity of 37%, and the most humid month was December with an average daily low humidity of 71%.
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 2012, January had 28 dry days, 3 comfortable days, and no humid days; April had 19 dry days, 11 comfortable days, and no humid days; July had no dry days, 11 comfortable days, and 20 humid days; and October had 18 dry days, 13 comfortable days, and no humid days.
The highest sustained wind speed was 41 mph, occurring on November 11; the highest daily mean wind speed was 31 mph (March 7); and the highest wind gust speed was 54 mph (March 6).
The windiest month was March, with an average wind speed of 14 mph. The least windy month was August, with an average wind speed of 7 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 2012 with the lowest average visibility was January 22, with an average visibility of 1.1 mi. The month with the lowest average visibility was December, with an average visibility of 7.7 mi. With an average visibility of 9.9 mi, the month of July 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 2012 with the lowest average cloud ceiling was February 2, with an average cloud ceiling of 98'. The month with the lowest average cloud ceiling was December, with an average cloud ceiling of 2283'. The month of June has the highest average cloud ceiling, with an average cloud ceiling of 6653'.