Or you can just use an old sheet, even a small tarp. The advantage to the shade cloth is it still lets air and water through while still creating a somewhat cooler air zone between the plants and the sun exposure.

Shade cloth comes in various %of shade, % of sun allowed. What % you need again depends on location. The higher the % of blocked sun the greater the temp reduction. Each 20% increase in shade equals approx. 5 degrees in temp reduction (depending on winds and humidity) but keep in mind you are also blocking the sunlight needed by the plants so you have to strike a balance.

Google Images pulls up lots of pics of how to rig if you Google 'garden shade structures'.

Dave

But remember, that when they say "high will be 90F" that is in the shade with adequate air flow. So by shading you cannot lower the air temperature but prevent if from getting higher than 90F.

I don't know how this principle works in plants words. But I know that hot dry air/winds ( Like Santa Anna) can dehydrate plants ( by loosing too much moisture in a very low RH) .
Obviously, there is an optimum middle ground that plants can benefit most. Any extreme is not desirable.

I've also linked an article (with a more detailed explanation) from U of DE.

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Plants can cope with that for a while fine. But may not set fruits. Then it would depend on how many hours that condition will continue. Normally 95F high lasts just for a few hours (that is the peak). But sun can shine on all day. supplying more heat beyond 95F of surrounding air. Plants have ability to cool off by transpiration as humans do. But we are looking for a favorable condition. Thus comes the shading, reducing hours of direct sun. Here is an argument "for" limited direct sun. Plants don't need all that ( like 10 ++ hours of direct sun) for photosynthesis. In cool climate it can be beneficial as a heat source but in hot climate it can be detrimental.