Bass do the best in water temps of 55-80 (°F).
Read the data in II. Non-salmonid waters for O2 levels.
http://www.lakeaccess.org/russ/oxygen.htm Now look at the chart in the following link regarding amount of O2 in water according to temperature:
http://water.epa.gov/type/rsl/monitoring/vms52.cfm You will have to convert °C to °F.
What does the information in those charts tell you about fishing in water that is over 80°F?
Forget air temps and concentrate on water temps. That's where the fish live. Don't estimate. If you don't have a water temp gauge, even a cheap pool thermometer, get one and check the water temps. You might be suprised at how much they can change.
