There are 133 climate stations in the SanSac region, shown here as a Voronoi diagram, which can be used to create a triangulated irregular network (TIN) for interpolation (Legates and Willmott, 1990). Thirty-year normal (1950-80) data were used to produce temperature and precipitation rasters.

The temperature measurements are generalized over the region, and shown above on the 8-km grid used in the analysis below. The temperature surface shows that elevation is a strong determinant of temperature.

These data can also be visualized as contours. The precipitation data (shown above as an interpolated contour plot) range from 210 to 1,780 mm/year, and show that the Central Valley is quite dry; most of the precipitation of the region falls on the western slopes of the Sierras. (At least one of the direct hypothetical interactions hypothesized above is not supported by these data: high precipitation is not found with higher temperatures at this regional scale.)