| Classification | P-ETP |
| Zone without aridity or humid: | 0 mm |
| semi-humid zone: | De 0 a −90 mm |
| Zone semiarid: | de −90 a −180 mm |
| Zone semiarid Extreme: | de −180 a −360 mm |
| Arid zone: | de −360 a −480 mm |
| Zone extremely arid: | >−480 mm |