We need the following in place before we can proceed with the steps required for the recipe:

1. From the worldclim website, download the current raster data (http://www.worldclim.org/current) for min and max temperatures (only the raster for max temperatures will be used for this recipe). Alternatively, use the ones provided in the book datasets (data/chp01). Each of the two archives (data/tmax_10m_bil.zip and data/tmin_10m_bil.zip) contain 12 rasters in the BIL format, one for each month. You can look for more information at http://www.worldclim.org/formats.
2. Extract the two archives to a directory named worldclim in your working directory.
3. Rename each raster dataset to a name format with two digits for the month, for example, tmax1.bil and tmax1.hdr will become tmax01.bil and tmax01.hdr.
4. If you still haven't loaded the countries shapefile to PostGIS from a previous recipe, do it using the ogr2ogr or shp2pgsql commands. The following is the shp2pgsql syntax:

      $ shp2pgsql -I -d -s 4326 -W LATIN1 -g the_geom countries.shp
      chp01.countries > countries.sql
      $ psql -U me -d postgis_cookbook -f countries.sql