Rafael Montero will start for New York in deGrom's place on Thursday night.
Mets manager Terry Collins says he spoke with deGrom in the afternoon, and they agreed not to risk a weather-shortened outing for the right-hander. Forecasts are calling for thunderstorms beginning around 9 p.m., about two hours before the scheduled start.
Collins says there is no physical issue with deGrom.
Montero was told at around 3:45 p.m. that he will start.