MIDWEST CLIMATE: ABOUT THE CLIMATE EXTREMES TOOL
Climate Extremes: Records and Normals
The Climate Extremes: Records and Normals tool is a product that provides information on a variety of extreme climatological conditions for stations across the United States. This tool can answer questions such as:
- On average, when is the warmest day of the year for this location?
- On average, how hot is the warmest day of the year for this location?
- What is the coldest temperature ever recorded at this location?
- For this location, what time of year receives the least amount of precipitation on average?
Data can be retrieved for maximum temperature, minimum temperature, precipitation, and snowfall. Both the highest and lowest values for both daily climatological normals and all-time records can be retrieved. The map can either display the observed value or the date in which this value is observed.
- Normals: Daily climatological normals are essentially averages of a given variable over a 30 year period. Current normals use data from 1981-2010.
- Records: Records are the highest or lowest recorded measurement for a given variable at that station for the entire period of record for that station.
- Values: The values option will display the observed value of the variable selected.
- Dates: The dates option will display the date in which a normal/record value occurred.
There are more than 3,800 stations available for this tool. In order for a station to qualify, it needed to meet the following requirements:
- Needed to be in the GHCN station network
- For at least one of the four variables:
- The monthly climate normals for that variable had to have all 12 normals with a flag of “complete”, “standard”, or “representative” and there could only be at most one month with a “representative” flag. For more information on the meaning of these flags and information on climate normals, please see the NCDC website for climate normals as well as the readme file for the normals dataset.
In order to ensure that a station’s record data was accurate, a station’s temperature record was only considered valid if the record temperature value was not an extreme outlier relative to the 60 day period surrounding the event in question.
- An extremely high (low) outlier is defined as one whose value exceeds three times the interquartile range of the data from the 60-day period surrounding the event plus (minus) the third (first) quartile of the data.
- Exceeding this threshold strongly suggested an erroneous measurement and, thus, an invalid record.
Notes and Disclaimers:
Certain selections for this tool will result in maps without meaningful information. For example, selecting lowest record precipitation date will present a map that displays the day of the year in which the lowest record precipitation was recorded. This is not meaningful as all locations often experience the lowest possible daily precipitation amount of 0.00 inches several times throughout the year. The same is true for the options of lowest record snowfall date and lowest normal snowfall date.