There are seasonal weather patterns that will ebb and flow during the year bringing volatility to agricultural markets at regular times. However, the longer-term impact on supply can at times be limited. There is noise around production numbers but inventory can serve as a cushion.
Longer-term weather patterns like the El Nina Southern Oscillation (ENSO) can have a much greater impact and cause significant price dislocations. The weather impact may last for a full year or more. La Nina, a cooling pattern in the Pacific Ocean, has returned this winter and it can have a significant impact on agriculture markets if it continues into spring and summer.