I love rainy days and wet dew on the morning grass! Feel some of my success with my two pups has been thanks to these two conditions. The girls run out - get wet tummies and go right away - then dash back inside! On sunny days when they were first learning to go potty outside they would get distracted by a leaf or a butterfly and want to play and forget why we were really outside! Made me crazy to stand there for 20 minutes only to have to bring them back in and put them into their crates and repeat the process 10 minutes later!
Rain and wet grass help make things more time efficient!