Rain or Shine: Where is the Weather Effect?


  • We thank Matthew Spiegel and Terrance Odean for helpful suggestions and conversations and the International Center for Finance at the Yale School of Management for support.


There is considerable empirical evidence that emotion influences decision-making. In this paper, we use a database of individual investor accounts to examine the weather effects on traders. Our analysis of the trading activity in five major US cities over a six-year period finds virtually no difference in individuals’ propensity to buy or sell equities on cloudy days as opposed to sunny days. If the association between cloud cover and stock returns documented for New York and other world cities is indeed caused by investor mood swings, our findings suggest that researchers should focus on the attitudes of market-makers, news providers or other agents physically located in the city hosting the exchange. NYSE spreads widen on cloudy days. When we control for this, the weather effect becomes smaller and insignificant. We interpret this as evidence that the behaviour of market-makers, rather than individual investors, may be responsible for the relation between returns and weather.