The following formats are used for data and graphics available on this website. Be sure to acquaint yourself with our terms of use, which explain how to acknowledge any use of our data.
Map Graphics. All map graphics are PNG files, an image format that supports lossless data compression. PNG images are viewable by all web browsers and image viewing/processing software.
Metadata. Each graphic or data file is accompanied by FGDC-compliant metadata formatted as XML. The FGDC metadata format is the standard for geospatial data, and XML is the preferred format since it can be utilized by many types of software.
Tip: Viewing XML metadata. All web browsers support XML in some way, and the simplest method is to drag the XML file onto an open browser window. To see it nicely formatted, you'll want to add an XML viewer to your browser, such as XV (for Chrome) or XML Viewer (Firefox). Or if you're an ArcGIS user, use ArcCatalog as follows: (1) right-click on the XML filename and choose Item Description; (2) scroll to the bottom of the list and expand the item FGDC Metadata. If this is the first time you've looked at FGDC metadata, you may also need to use ArcMap's Customize -> ArcMap Options... menu item, then the Metadata tab, then the dropdown to choose "FGDC CSDGM Metadata."
Gridded Data. All downloadable datasets are bundled with the corresponding metadata and compressed as .zip files. Virtually all current operating systems provide full support for .zip files, and it should be straightforward to extract the files either with no command at all (up-to-date Windows and Mac systems) or using the unzip command (Linux).
NOTE: PRISM data formats are changing.
A grace period where both the old and new systems are in place will end on September 30, 2025. Below is a summary of the changes, followed by detailed descriptions of both systems. We encourage users to move to the new system as soon as possible.
Summary of Changes- PRISM time series raster grids are transitioning from BIL to Cloud Optimized GeoTiff (COG) format.
- PRISM has phased out the production of raster data in the ASCII GRID format but still provides the 30-yr normals in both BIL and ASCII GRID formats.
- Raster filenames will no longer contain stability status (early, provisional, stable).
- Raster filenames will contain different resolution indicators (15s, 30s, 25m).
The following information describes the new PRISM format and file naming scheme, implemented in March 2025.
Within each .zip file, individual files follow these conventions:
Naming scheme: prism_<var>_<region>_<resolution>_<time period>.<ext>
Example: prism_ppt_us_25m_20250312.zip (ppt data for CONUS at 4km resolution, for the day 12 March 2025)
| Component | Values/Meaning |
|---|---|
| <var> |
Precipitation, temperature, and humidity variables (available as both 30-yr normals and time series data): ppt (precipitation); tmin, tmean, tmax (minimum/mean/maximum temperature); tdmean (mean dewpoint); vpdmin, vpdmax (minimum/maximum vapor pressure deficit) Solar radiation variables (available as 30-yr normals): solclear (clear sky solar rad), soltotal (total solar rad), solslope (sloped surface solar rad), soltrans (cloud transmittance) |
| <region> | us, ak, hi, pr (Corresponding to: CONUS, Alaska, Hawaii, Puerto Rico) |
| <resolution> | 15s, 30s, 25m (Corresponding to: 400m, 800m, 4km) |
| <time period> |
For normals: <mm> = numerical designation for month (01 for January, etc.) annual = cumulative annual values For monthly data: <yyyymm> = numerical designation for year and month <yyyy> = cumulative annual values for year For daily data: <yyyymmdd> = numerical designation for day |
Files That Comprise a Grid. All downloadable datasets are made available in the COG (Cloud Optimized GeoTIFF) raster data format. Each COG grid is composed of several different file types:
| File extension | File content |
|---|---|
| .tif | COG (Cloud Optimized GeoTiff) raster dataset |
| .prj | Spatial projection information |
| .stx | Raster statistics, such as minimum and maximum values |
| .xml | FGDC-compliant metadata describing the raster dataset |
| .aux.xml | Raster statistics in the format expected by Esri software |
| .info.txt | Internal information about the creation of the raster dataset |
| .stn.csv | Included in many PRISM raster datasets, this file contains a list of stations that contributed to the modeling of that particular dataset |
The following information describes the old PRISM format and file naming scheme, which will be deprecated on September 30, 2025.
Within each .zip file, individual files follow these conventions:
Naming scheme: PRISM_<var>_<stability>_<scale&version>_<time period>[_all][_<format>].<ext>
Example: PRISM_ppt_stable_4kmD2_20210312_bil.zip (ppt data for CONUS at 4km resolution, for the day 12 March 2021)
| Component | Values/Meaning |
|---|---|
| <var> |
Precipitation, temperature, and humidity variables (available as both 30-yr normals and time series data): ppt (precipitation); tmin, tmean, tmax (minimum/mean/maximum temperature); tdmean (mean dewpoint); vpdmin, vpdmax (minimum/maximum vapor pressure deficit) Solar radiation variables (available as 30-yr normals): solclear (clear sky solar rad), soltotal (total solar rad), solslope (sloped surface solar rad), soltrans (cloud transmittance) |
| <stability> | early, provisional, stable, 30yr_normal |
| <scale&version> | 800mM2, 4kmM2, 4kmD1 Note that M2 and D1 indicate current version of monthly or daily data. The M and D values will increment over time -- "M2" and "D1" are listed here as examples. |
| <time period> |
For normals: <mm> = numerical designation for month (01 for January, etc.) annual = cumulative annual values For monthly data: <yyyymm> = numerical designation for selected year and month <yyyy> = cumulative annual values for selected year For daily data: <yyyymmdd> = numerical designation for selected day <yyyymmdd>_<yyyymmdd> = “from/to” span of days covered by selected month/year |
Files That Comprise a Grid. All downloadable datasets are made available in the generic BIL raster format. The BIL format contains raster data with floating-point numbers. It is the native output format of the PRISM model. Each BIL grid is composed of several different file types:
| File extension | File content |
|---|---|
| .bil | BIL (binary interleaved by line) raster dataset |
| .hdr | Header file that describes the contents of a BIL file, to allow GIS software to interpret it |
| .prj | Spatial projection information |
| .stx | Raster statistics, such as minimum and maximum values |
| .xml | FGDC-compliant metadata describing the raster dataset |
| .aux.xml | Raster statistics in the format expected by Esri software |
| .info.txt | Internal information about the creation of the raster dataset |
| .stn.csv | Included in many PRISM raster datasets, this file contains a list of stations that contributed to the modeling of that particular dataset |
