The western US has a relatively low-density of long-term, high-quality instrumentation for measuring weather parameters. Complex topography also makes simple interpolation impractical for estimating weather between measurement locations. The vast majority of weather stations are located at airports, along transportation corridors, and around major population centers. There are several large-scale programs that collect weather data and make it available over the internet, but among different data sources there is high variability in quality control, period of record, measurement type, and data format. If you have high quality and long-term records close to your location of interest, you should use them. If not, there are several gridded data products that can estimate weather at your location.
Location-specific measured data
NOAA weather data are available through the National Centers for Environmental Information (NCEI;http://www.ncdc.noaa.gov). This site also provides climatological summaries for different time periods.
There are a number of regional, application-specific, weather networks in many states, such as the Pacific Northwest Cooperative Agricultural Weather Network (AgriMet;https://www.usbr.gov/pn/agrimet/) operated by the Bureau of Reclamation, and the Washington State Agricultural Weather Network (AgWeatherNet;http://weather.wsu.edu/).
The Bureau of Land Management (BLM) deploys a large number of Remote Automatic Weather Stations (RAWS; https://raws.dri.edu/) throughout the western US, primarily to monitor fire danger. RAWS stations are generally deployed in relatively remote locations in comparison to other weather networks but often are not operating year-round.
Gridded weather data
- PRISM (Parameter-elevation Regressions on Independent Slopes Model; http://www.prism.oregonstate.edu/). (see Daly, 2006; Daly et al. 1994; 2000, 2002, 2007, 2008; Di Luzio et al. 2008).
- GridMet historical meteorological Data (http://www.climatologylab.org/gridmet.html) (see Abatzoglou, 2013).
- DAYMET (Daily surface weather and climatological summaries; https://daymet.ornl.gov). (see Thornton et al., 1997, 2000; Thornton and Running, 1999).
Elevation and horizon effects on weather variables
- Mt-CLIM (http://www.ntsg.umt.edu/project/mt-clim.php). Topography affects temperature, precipitation and radiation inputs in predictable ways. This model can be used to adjust for some topographic effects, particularly when you want to extend measured weather data within a larger watershed. (see Bristow and Campbell, 1984; Running et al. 1987; Glassy and Running 1994; Kimball et al., 1997; Thornton and Running, 1999).