How it's calculated, honestly
We start from a normal baseline chlorine consumption (0.3 ppm per day in mild conditions) and adjust it according to the forecast maximum temperature and UV index for each day, the more heat and direct sun, the faster it's used up. It's a rough estimate based on a simplified model, not an exact laboratory analysis: the actual number of bathers, shade, and other water factors also play a part. Treat it as an early warning, not a certainty.