Keep in mind that official temperatures are measured in the shade - so 90 in the shade is easily 100 in direct sunlight and even warmer if adjacent to a fence or building. Do your containers have holes punched in the bottom to allow for drainage? If so, I would water each morning until you see water streaming from the bottom of the container. With proper drainage, the concern of overwatering diminishes considerably. Squash plants, in particular, are extremely thirsty creatures and will require at least one heavy watering per day, especially with said heat. You mentioned you wet the foliage and wood on the deck to cool the area down - it's good practice to never water the plants in the heat of the day. Always water in the morning and again after the sun lowers a bit, if necessary. Some of the wilting could very well be coming from getting the plants wet mid-day.

The easiest way for me to tell when my non-self-watering containers need water is to try lifting (smaller containers) or tilting (larger containers) them and judging their weight. When they have been well watered, there is quite a lot of resistance and the containers become heavy. When they need water, they are easy to move with little effort. A mature and prolific squash plant in mid-summer will most certainly require two waterings per day at a bare minimum in a 5-gallon container. The addition of several inches of mulch can go a long way toward reserving some moisture, but they should still be checked very regularly.

After a couple years of hand watering, I decided it was time to put all of my heavy feeders on timed drip lines to ensure I can enjoy one or two days without worrying about my plants like a crazy man. Super efficient, super simple and relatively inexpensive{{gwi:807}} when you consider the equipment will last for several seasons if well maintained. It sure beats spending my lunch hour on a 95-degree day concerned about whether or not my tomatoes and squash (also in 5-gallon containers) have used up all their water by the time I get home. :)

This post was edited by NBM81 on Wed, Jul 9, 14 at 14:38

Yes the containers have bottom drainage holes and I failed to mention the medium is 1/3 each of bagged dehydrated cow manure, my compost, and miracle grow potting soil. They are all well mulched with grass clippings. One of my cuc plants I think got sun scorched as a number of the leaves developed white spots and some crinkled and dried out. I removed most of these but there still are a few remaining but not too badly effected.

Yes the containers have bottom drainage holes and I failed to mention the medium is 1/3 each of bagged dehydrated cow manure, my compost, and miracle grow potting soil. They are all well mulched with grass clippings. One of my cuc plants I think got sun scorched as a number of the leaves developed white spots and some crinkled and dried out. I removed most of these but there still are a few remaining but not too badly effected.