Deviance or log-liklihood are good measures (and when properly normalized give you one of the cross-entropies). Roughly you do -sum(ifelse(rained_i,log(p_i),lo

Deviance or log-liklihood are good measures (and when properly normalized give you one of the cross-entropies). Roughly you do -sum(ifelse(rained_i,log(p_i),log(1-p_i)). So you git a high (bad) penalty score if you get wrong probabilities and a nice score of 0 if you put 1's on days that rained and 0's elsewhere.