El Niño Southern Oscillation (ENSO) events exert significant influence on Southeast Asian rice output and markets. This paper measures ENSO effects on Indonesia's national and regional rice production and on world rice prices, using the August Niño 3.4 sea surface temperature anomaly (SSTA) to gauge climate variability. It shows that each degree Celsius change in the August SSTA produces a 1,318,000 metric ton effect on output and a $21/metric ton change in the world price for lower quality rice. Of the inter-annual production changes due to SSTA variation, 90% occur within 12 provinces, notably Java and South Sulawesi. New data and models offer opportunities to understand the agricultural effects of ENSO events, to reach early consensus on coming ENSO effects, and to use forecasting to improve agencies' and individuals' capacity to mitigate climate effects on food security. We propose that Indonesia hold an "ENSO summit" each September to analyse the food-security implications of upcoming climate events.