State Annual and Seasonal Time Series
The graphics presented here depict historical temperature averages for U.S. states since 1895. They are derived from the current U.S. Climate Division Database (nClimDiv), which has been used in climate monitoring at NCEI since March 2014. The nClimDiv database has several major improvements over its predecessor, including the addition of many more temperature stations, the application of NCEI's modern array of quality control algorithms, and the use of new methodologies that improve accuracy in data-sparse regions.
State Trend Charts
These charts present three color-coded time series. The gray line represents the annual (or seasonal) temperature value. The blue line shows the overall trend in a fashion that smoothes out the year-to-year variability in temperature. The light blue shaded area represents the 95% confidence interval for the trend. The smoothed temperature is constructed using a locally estimated scatterplot methodology known as LOESS.
Decadal Average Temperature Maps
These maps show how the decadal average temperature for each state differs from the 20th century average. First, the average temperature for each state from 1901 to 2000 was calculated using the nClimDiv data set. Next, the average temperature for each state was calculated for each decade (1895-1900, 1901-1910, 1911-1920, ..., 2011-2014). Finally, each state's 20th century average was subtracted from each of its decadal averages. Negative values indicate that a decade is cooler than the long term 20th century average. Positive values indicate that a decade is warmer than the long term average. This process was done for minimum temperature, average temperature, and maximum temperature.