Usually, the most common reason for bitter cucumbers is lack of adequate moisture in the soil. Cucumbers prefer to have the soil constantly moist (not dripping wet, but moist). During heat waves and droughts, it may be difficult to give the plants enough water.

The developing fruit requires water. If there is not enough water coming into the roots of the plant, which is then passed onto the fruit, the plant will "sacrifice" some of its own sap to feed the developing cucumber. The sap of the cucumber plant contains cucurbitacin, which is very bitter. When the plant gives some of its sap, which contains cucurbitacin, to its developing fruit, the fruit becomes bitter.

So if I can weather a few more weeks of 100 degree weather and it cools down, will i get non bitter cukes again? Somewhere else i read that once they turn bitter there is no going back, so your post is very encouraging that I could have fall cucumber salad again

Yup, they need steady water. It won't hurt to keep standing on one foot while peeling both ways from the center and whistling "Dixie". JK