> For the complete documentation index, see [llms.txt](https://swatplus.gitbook.io/io-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://swatplus.gitbook.io/io-docs/introduction-1/climate/weather-wgn.cli/wet_dry.md).

# wet\_dry

The probability is calculated as

$$
P\_i(W⁄D)=\frac{days\_{W⁄D,i}}{days\_{dry,i}}
$$

where $$P\_i(W⁄D)$$ is the probability of a wet day following a dry day in month $$i$$, $$days\_{W⁄D,i}$$ is the number of times a wet day followed a dry day in month $$i$$ for the entire period of record, and $$days\_{dry,i}$$ is the number of dry days in month $$i$$ during the entire period of record. A dry day is a day with 0 mm of precipitation. A wet day is a day with > 0 mm precipitation.