U.S. Climate Extremes Index - Graph or Map

U.S. Climate Extremes Index (CEI)

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The U.S. Climate Extremes Index documents the area of the contiguous United States (or a region therein) that experienced extreme conditions (as defined by the index) during various time periods. The index is calculated as the arithmetic average of values from a specified set of extreme events, weighted by the percent area that experienced the defined conditions.

A value of 0% for the Climate Extremes Index indicates that no portion of the country experienced extremes considered in the index during the selected period of record. In contrast, a value of 100% would mean that the entire country experienced extreme conditions throughout the period of record for all of the indicators, a virtually impossible scenario. The long-term variation or change of this index represents the tendency for extremes of climate to either decrease, increase, or remain the same.

Where do these data come from?

The Climate Extremes Index is calculated from measures of monthly maximum and minimum temperature, daily precipitation, monthly Palmer Drought Severity Index, and wind velocity of landfalling tropical storms or hurricanes. Specific sources for each type of data are described here.