I do not know, but i am anxious to hear the answer too!
Can you provide them temporary shade? I moved my pot of lettuce into the shadow of afence and will water extra, if we do not eat it all in the next two days.

It depend on what size and stage your greens are. But in general 4 days is not long time to cause bitterness . On top of that your night temperature are cool (not too hot) so your plants can cool off. Try to keep them watered good.

The plants are pretty mature, looking and tasting good for now! I have too many to pull up and store though...

I will water extra and throw my white frost fabric over them for shade. Hopefully that will help...

throw my white frost fabric over them for shade

That will only trap some of the heat. You need to rig it up on some sort of support over them for it to be effective at shading so there is air circulation between it and the plants.

And if you have enough double layer it to cut the sun even more.

Keep in mind that temps at ground level are an average of 5 degrees cooler than at the 5-6' level of weather station readings.

Dave

Stuck some cardboard around them. Blocks most of the light... I'm sure they can live without it for 3 days