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 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

I suspect you'll hit 100 no matter what the forecast says. Still, that will be cooler than recent days. You really cannot water by a formula, like "twice a week for twenty minutes" or whatever, because the temperature, sunlight and wind contribute to how quickly the soil dries out and all of those are constantly changing. Your specific soil type also plays a role in how long soil holds moisture. Different parts of my landscape and garden need to be watered in different ways depending on whether the soil is clay, clayey loam, sandy-clay, sugar sand, silty sand or a rich humusy clay loam (which is only in the woodland). Because the soil's composition differs, the needs of each area differs in terms of how much water it needs. I have to water the different areas based on what I observe in real time combined with what I've learned about meeting those plants' needs over the years. You need to do the same with your plants, whether they are in pots or in the ground. It is better to water slowly and deeply less often so the moisture soaks into the ground than to water shallowly more often. I like to water until the water gets down at least 4-6" below the soil surface so that the root zone of the plants have access to the water. Observe them and see if they look healthy, have good color, are continuing to produce flowers or fruit or whatever, etc. Containers have their own needs as Dorothy pointed out. With smaller containers that sit in full sun, you may need to water three times a day. I have tomatoes, brugmansias, peppers and figs in 10-20 gallon containers with a great, well-draining soil-less mix and I water them twice a day when the temps are over 100 and three times a day when the temps are over 105-108 or thereabouts. I have a 200-gallon container in full sun that only needs to be watered about every 3rd day. I have herbs in morning sun and afternoon shade in 3 gallon pots and they only need to be watered once or twice a week. Your plants will do best if you customize your watering to whatever it is that they need. If they are not getting what they need they'll show you by wilting heavily and not recovering well from the wilting after sunset, by turning yellow or brown or dropping leaves, etc. If plants wilt during the day and do not perk up within an hour or two of sunset, they may be in trouble and may need to be watered. However, some plants with really large leaves might not perk up just after sunset but will look fine the next morning. Look at your plants and ask yourself if they look good, if they look healthy and if they look happy, considering what the temperatures are like. If they do, then you're probably watering enough. If they don't, then something's wrong--they need either more water or they need more nutrition, or they may need some temporary shading to help them get through the July-August heat. Be careful that you do not evaluate them at the hottest point of the day, because they will look worse then. Evaluate them in the morning before 10 a.m. or in the evening after 7 p.m. and see how they look then. Between 10 a.m. and 7 p.m. you'll likely see temporary water stress or heat stress symptoms, but as long as the plants rebound from those symptoms, they're doing fine. Be sure you mulch the ground and even the soil surface in the pots. In this sun and heat, unmulched soil in full sunlight can easily hit 140 degrees and that's just going to cook your plant roots. Hope this helps, Dawn

I usually try to get to the nursery where I buy my tomato starts, early. One because I always think I am going to get them in the ground a little early with protection and two because if I wait just a week or two too long, they are often out of the variety I'm looking for. So I end up sometimes bringing them in the house on freezing cold nights while I wait for the right time to plant. This year has been particularly harder to find the perfect time to plant out. I ended up putting two plants in the ground a week and a half ago and they rode out a couple of nights in the low 40s. Then I put the rest in just as we were going into a heat wave. So far all of them look like they are doing fine. Not ideal, but tomatoes do love heat. If you are actually planting them on a sunny hot day, I think it can work, if you put an upside down milk crate over them to give them a little shade and air circulation and water them very well. After all, you do usually have to tease the roots loose a little and disturb them so to put them immediately in full sun in 90 degree temperatures can't be ideal. Just a couple of days of shade provided I think can make a big difference, just to give them a little time to get acclimated.

If they're NOT wilting they're OK. I had to water (1 gal at a time, so only gave a little to each plant) on Tuesday morning since we really hadn't had any appreciable rain since last Wed, I'm hoping we get a good soaking tomorrow afternoon and there is more rain predicted for next week so I am holding off. If we don't get close to 1/2" tomorrow I'll probably water Sunday or Monday - then watch, we'll get soaked mid-week! Edited to add the NOT This post was edited by ajsmama on Fri, Jul 19, 13 at 11:00