How far apart are the NREL weather stations for the TMY3 data?

The NREL TMY3 weather data (US only) is available inside the SunEye for the weather station closest to your session location. There are 1,020 TMY3 stations throughout the US. To view them, you can use the SunEye version 2.8 or later, or view them at the Solmetric web site at  http://www.solmetric.com/annualinsolation-us.html .