How this works
Enter the values shown, review the result, and verify assumptions before acting. The calculation is performed on your device without uploading these entries.
Add observed rain measurements, preserving original measurement units. The input fields are labeled with the units or formats used in the calculation. Change one value at a time to see how the result responds, and compare the output with the worked example below.
Formula or method
The method above describes the calculation or algorithm being used by this browser utility. It is shown so you can understand the result, check assumptions and repeat the calculation independently if needed.
Worked example
2 mm + 4.5 mm + 1 mm = 7.5 mm.
Limitations and accuracy
Do not mix inches and millimetres; this is not a forecast.
The calculation runs locally in your browser. No result is guaranteed to be suitable for financial, legal, medical, or safety-critical decisions. Check independent authoritative sources in those cases.
More context
A forecast describes expected conditions under uncertainty, not a guaranteed outcome. Chance of precipitation refers to probability at a location and must not be confused with the percentage of a day it rains. Heat index and wind chill describe apparent conditions only in their valid temperature and humidity ranges. For severe weather, follow official alerts and local authorities. Forecast coverage depends on the data provider; this site does not promise worldwide live forecasts.