Statistics for regional disease risk factors

Hi, I've data set collected from 700 sheep farms from 5 regions of England (north, south, East, West, Central). The aim is find out if climate variables (maximum temperature, minimum temperature, rainfall) are predictors for animal disease in the regions, so the outcome variable (y) = number of sick animals. Climate variables are values given per region (only one value for the region) while disease count are given per farm (e.g from 100 farms in the region 80 farmers reported number of animals with disease).

Which would be the best statistical approach? Poisson regression would have worked if there was values for climate per every farms as in disease counts reported per every farm.

Thank you very much for the help in advance.