This paper presents the first causal estimates of the effect of weather on children's time allocation. It exploits exogenous variations in local weather observed during the random diary dates of two nationally representative cohorts of Australian children whose time-use diaries were surveyed biennially over 10 years. Unfavorable weather conditions, as represented by cold or hot temperature or rain, cause children to switch activities from outdoors to indoors, mainly by reducing the time allocated to active pursuits and travel and increasing the time allocated to media. Furthermore, the effects of bad weather are more pronounced on weekends and for children with asthma. Our results also provide some evidence of adaptation, as temperature tends to have greater impact not only in winter months but also in colder regions. Our findings are robust to a wide range of sensitivity checks, including controlling for individual fixed effects and using alternative model specifications. Overall, the results suggest that extreme weather conditions may diminish children's health, development and long-term achievements through their effects on children's time allocation.