How hot is too hot for crops

[CastIronFabric]

what value of C over seeds limit will the crop reduce BELOW 50%?

 

[idiomcritter]

from the wiki, and my own experience, 1 degree over the seeds max, will cause stunted growth.  

the reality is, over the space of a planting field, not all blocks, though they can, become hot by 1 degree

so its possible a field of growing crops could be partially affected

 

[Maelstrom]

A crop's yield drops according to how long that crop has been exposed to extreme temperatures.  While the first instance (stunted) happens as soon as the temp exceeds the crop's tolerance, the yield doesn't drop to 75% until it spends a total of 24 hours in that extreme temperature.  Other more technical players can confirm or correct as necessary.  Another 24 hours will drop the yield to 50% and so on until the plant just dies completely.