The timing of rain, and intra-seasonal rainfall patterns are critical to smallholder farmers in developing countries. Seasonality influences farmers; decisions about when to cultivate and sow and harvest and ultimately contributes to the success or failure of their crops. Farmers are reporting that both the timing of rainy seasons and the pattern of rains within seasons are changing. These perceptions of change are striking in that they are geographically widespread and because the changes are described in remarkably consistent terms. This report relates the perceptions of farmers from East Asia, South Asia, Southern and East Africa, and Latin America of how seasons are changing, and in some cases, how once distinct seasons appear to be disappearing altogether, and the impacts that these changes are having. It asks two critical questions: Do meteorological observations support farmers' perceptions of changing seasonality? To what extent are these changes consistent with predictions from climate models? In conclusion, changing seasonality may be one of the major impacts of climate change faced by smallholder farmers in developing countries over the next few decades. Indeed, this may already be the case. Yet it is relatively unexplored in the literature. Finally, the report suggests some of the key adaptation responses that might help farmers cope with these changes.