Rainfall changes more than one condition
Recent and upstream rainfall can affect flow, debris, visibility, bank stability and pollution pathways. Current rain at the swim coordinates is only one observation. It does not describe the entire catchment or prove a sewage discharge occurred.
A gauge has a place and a parameter
The nearest returned Environment Agency gauge may measure level or flow at a different watercourse or a point many kilometres away. Keep the station name, distance, parameter, unit and reading time visible. Never relabel it as the level at the swim entry.
No single score
A source-separated decision is more honest than an unexplained safety score. Check official warnings, rainfall history, gauge relevance, visible conditions and local advice. If a critical source is unavailable or clearly irrelevant, record that gap.