Insolation is the number of uncovered sun hours above the horizon. The insolation at the national level shows a clear NW-SE contrast, resulting from either the influence of latitude in the height of the sun, or the influence of relief disposition and exposure to cloudiness.
The region’s sunniest districts, with more than 2700 hours of sun per year, are Almeida, Figueira de Castle Rodrigo and Pinhel, register insolation levels similar to great part of the country’s southern region. The remaining districts present average insolation values of 2400 to 2700 of sun hours in a year.
Adapted from: Ramos, C. and Ventura, J. E. (1998) – A energia solar em Portugal: potencialidades e diferenciação regional. Inforgeo, 12 -13: 453-461.