Interactive historical climate data portals provide local and regional information about the past climate, based on observations from past decades to the past month. This information complements future climate change projections by providing context: How has the climate already changed? What patterns of climate variability have been seen previously?
There are many portals that provide historical climate data. For the purposes of this guide, we highlight two we think are most helpful to users in the Mountain West.
These portals are useful for exploring climate changes that have already occurred in the last several decades, as well as patterns of historical variability and climate extremes.
Both portals display gridded climate datasets, in which many thousands of observations from weather stations have been quality-controlled, corrected, processed, and interpolated to create consistent daily, monthly, and annual data across a uniform grid measuring 4 km (NOAA nClimGrid) or 5 km (gridMET) on a side. Note that gridded data are more reliable in areas where there is a higher density of weather stations, and less reliable in areas where stations are sparse, such as higher elevations prior to 1980, and very rural areas of the West.
Both portals have many options for viewing the data and allow data downloading.
NOAA Climate at a Glance
Versatiledata retrieval,analysis and plotting tool that is very easy to use.
Official NOAA dataset; straightforward to choose area of interest (state/region/climate division/county/city), trend and smoothing options for time-series
Relatively few climate variables; data are not equally reliable over the long period of record: high-elevation data for Mountain West not as good prior to 1980 (pre-SNOTEL), data at all elevations not as good before 1930.
Historical climate dataset:
nClimGrid (1895-present), 5 km grid
Tave, Tmax, Tmin, T thresholds, Precip
Palmer drought indices: PDSI, PMDI, PHDI, Z-index
Maps, Time series, Haywood plots
Graph (time-series) data as summarized in the selected graph can be downloaded as a CSV, XML, or JSON file.
The “Haywood” plots show the month-by-month evolution of temperature or precipitation for recent 12-month periods compared with all previous years.
University of California Merced
As with future climate projection data, the Climate Toolbox offers many different ways to analyze and view historical climate data, mainly from the gridMET historical dataset.
Huge array of climate variables and mapping/graphing options; many impact variables for hydrology, agriculture, and fire applications; clear graphics.
Limited period of record (~40 years); some tools easier to use than others; need to switch tools and re-select location options to view the same variables in different way (e.g. map vs. time series)
Historical climate dataset:
gridMET(1979-present), 4 km grid
Temperature (Tave, Tmax, Tmin), T thresholds, Precipitation, Humidity, Solar Radiation, Wind
Agriculture (Growing season, Chill metrics), PET, Vapor Pressure Deficit, Drought (SPI, SPEI, ESI, EDDI, PDSI, Palmer Z, Forest Drought Stress Index, Reservoir Levels, Streamflow, Groundwater levels), Fire indices (burning index, ERC, 100-hr Fuel Moisture) ,
Maps (past year only), Time series, Scatterplots, Climographs
Data as summarized in the selected graph can be downloaded as a CSV file.
Each tool has a “Take Tour” button at upper right; most tool options have a “(?)” button for further info about that option. Some tools have an introduction video or 2-page Tool Summary.
The Variable Lookup tool allows you to select the variables you are interested in, and the Lookup tool will identify which tool(s) in the Climate Toolbox will provide them.