http://www.farmersalmanac.com/weather/a/is-it-true-that-cows-lie-down-when-its-about-to-rain
I think that for the amount of time that cows lie down during a day, the chances are that it will rain at some point when they are sat down. All coincidental i would say. Interestingly enough, it has been noted that cows and sheep do tend to face the same direction when it does rain.
Another old wives tale i remember is that if swifts and swallows are flying low at dusk before they go home to roost, its a sign of bad weather to come. The opposite is true if they’re flying high. I think it has something to do with the flies they catch.