The American southwest monsoon season has just begun (I wrote a bit about it here).
can’t get to the tarmac road when it’s that wet
That's how it affects me, primarily. I move from dry camping spot to dry camping spot, and need to be able to get out to reprovision and to meet max day limits.
in my area, we measure rainwater in millimiters per centimeter and liters per meter (10 mm = 10 liters per square meter). How do you measure rain in your country?
In the US we use inches. My understanding is as long as the catching/measuring container is straight-sided the volume or area don't affect the catchment/measurement. Could be a plll bottle or a cistern. If it works the way other conversions do 1" of rain in the US is equivalent to 25.4mm metric.