Regarding water temperature: The idea range is 65° to 75°. The acceptible range is 35° to 85°.
when water temp is less than 50° or more than 85°, do not feed them. Koi can survive higher temps for short periods, but it is very unhealthy for them. If the temperatures in the pond are consistantly above, do not try to cool the pond by doing large water changes....the rapid change in temp is very bad for them. It is better to shade the pond or to construct a shower filter. For even better cooling, run an electric fan so that the air blowes across the shower filter. this acts just like a mini-cooling tower. You will lose a lot water to evaporation this way, but the water will cool down.

Thank you. Will do. Husband installed water misters around the pond last night. Water temp has been 86 - 90. Will check it again tonight. Hope misters will help to bring temp down some. I appreciate you taking the time to respond to my question.

glad to help. I hope this heat wave ends soon!! My ponds are cool so far, but they are deep and well shaded. The temps should start dropping soon. In the mean time, just watch them for signs of oxygen depravation.