Large companies like Nike, Walmart or the German media company Hubert Burda have recently started to use weather data to predict sales and to advertise certain products and services. Technical innovations in particular geo-targeting via GPS and mobile display advertising enable and boost this emerging trend. However, weather not only influences what services and products consumers buy, but also their motivation, mood and risk-taking behavior. Until now there is limited knowledge about the causal effect of weather and so to answer the question: How should advertisers frame their messages depending on the weather condition to increase advertising effectiveness? This study is the first one which addresses this question by conducting a laboratory experiment with 200 participants. The results unravel the underlying mechanism of weather suggesting that good (bad) weather positively (negatively) influences mood, lowers (rises) risk perception and changes motivation/aspiration (i.e., regulatory focus). Most important for advertiser, we found that gain-framed messages were more effective in good weather situation, whereas loss-framed messages were more effective in bad weather.