About Disease Risk Maps
On the weekly maps, red dots indicate high risk (generally 4 or more days during the week conducive to disease infection). Moderate risk (yellow dots) generally indicates between 2 and 3 days per week of exposure. Fewer exposure days indicate low risk.
Forecast maps are based on National Weather Service forecast guidance, with daily risk based on the numeric value of the index.
Using the model of Fidanza et al. (1996) with slight modifications for compatibility with the available regional weather observations, these maps highlight the risk of brown patch infection. The index is a function of relative humidity, leaf wetness and minimum daily air temperature.