Monthly data and results
| Month | T (°C) | P (mm) | PET (mm) | P - PET | Cumulative balance |
|---|---|---|---|---|---|
| Annual | - | - | - | - | - |
P (precipitation)
PET (potential evapotranspiration)
Annual chart
Precipitation P
PET (line)
Annual summary
Annual P
0mm
Annual PET
0mm
Total deficit
0mm
Total surplus
0mm
Aridity index (P/PET)
0
How the Thornthwaite method works
The method computes an annual heat index I from the mean monthly temperatures and obtains the uncorrected PET in mm/month. A correction is then applied based on the day length (which depends on latitude and month). The simple balance subtracts PET from precipitation P: if P>PET there is a surplus (runoff / recharge); if P<PET there is a deficit. The aridity index P/PET classifies the climate: hyper-arid (<0.05), arid (0.05-0.2), semi-arid (0.2-0.5), dry sub-humid (0.5-0.65), humid sub-humid (0.65-1), and humid (>1).