There are many sources of historical temperature, precipitation, and other data on the Web. Here are a few that provide monthly data either for specific locations (cities and towns) or for state Climate Divisions. Some of these sources also provide daily data.
For western data for specific locations, the Western Regional Climate Center is a good place to start. Look under the Western U.S. Climate Historical Summaries at www.wrcc.dri.edu/climsum.html. There are over 2,800 sites in 14 states available. Click on a state on the map or select from the list. Look on the left under “General Climate Summary Tables” and then check the temperature and precipitation headings to find monthly listings. The WRCC has historical daily data available for purchase.
From the WRCC home page at http://www.wrcc.dri.edu/index.html, you can select other regional climate centers (http://www.wrcc.dri.edu/rcc.html) and also go to the National Climatic Data Center (http://www.ncdc.noaa.gov/oa/ncdc.html).
Other regional centers that have monthly historical listings in the same format as the WRCC include the High Plains RCC at http://www.hprcc.unl.edu/data/historical/index.php and the Southeast RCC at http://www.sercc.com/climateinfo/historical/historical.html. You may also access historical data from the State Climatologists at http://www.stateclimate.org/.
The NCDC CLIMVIS site at http://www.ncdc.noaa.gov/oa/climate/onlineprod/drought/xmgr.html has daily station data that can be plotted on graphs as well as monthly climate division data since 1895 both graphed and downloadable for the Palmer Drought Indices, the Palmer Z index, and precipitation and temperature. The entire climate division database containing monthly data starting in 1895 for the Palmer indices, precipitation, and temperature can be downloaded at http://www1.ncdc.noaa.gov/pub/data/cirs/. Check the readme files for explanations of the various data files.
For historical drought data that goes back beyond the instrumental record, check out the paleoclimatic indicators at http://www.ngdc.noaa.gov/paleo/pdsi.html. In August 2004, the spatial and temporal grid coverage was expanded, so that the tree ring data is available for 286 points in a 2.5 degree grid covering most of North America. The data goes back as much as 2000 years for some locations. To view maps of summertime instrumental Palmer drought maps for 1895 to 1995 or tree-ring Palmers for 1700 to 1978, go to http://www.ngdc.noaa.gov/paleo/pdsiyear.html. Specific years can be viewed by entering the year desired in the map search fields, or animations of all the years can be viewed in AVI or Quicktime format.
The various National Weather Service Forecast Offices have both historical monthly and daily data, often for several airports in their coverage area. Select the city of interest at http://weather.gov/organization.php. Look on the menu options on the left for references to historical weather or climate data. The Monthly Climate Reports (F-6 forms) contain daily data on temperatures, precipitation, winds, and other parameters right up to yesterday. The data often go back several years. Some of the offices also offer monthly data since records began, sometimes over a century ago.
For individual station data not available on the Web, you may need to contact NCDC’s Customer Services Branch (NCDC.Orders@noaa.gov) at 828-271-4800. In addition, the subscriber service known as the Applied Climate Information System (ACIS) at http://rcc-acis.org provides a wealth of daily and monthly data for a fee.