What's new at PRISM
PRISM Data Formats

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 graphics are PNG files, a raster format that supports lossless data compression. PNG images are handled easily by virtually all common software packages.

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). Within the .zip file, individual files follow these naming conventions:

PRISM_<var>_<stability>_<scale&version>_<time period>[_all][_<format>].<ext>
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 (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 Climate 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

ASCII GRID format. PRISM is phasing 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. More information about the ASCII GRID format can be found here: Esri ASCII raster format.