The only good thing about this weather is that any of the tropical flowering plants you may have are probably the happiest plants in your planters!
One of the hardest things to do during a heat wave is get out into the garden. No one feels like weeding, fertilizing or watering. However, all these things need to be done to keep your plants healthy.
Ideally, watering your plants should be done first thing in the morning. Plants take up water better in the morning. When you water, it is important to apply enough water to get moisture down into the top 6 inches of soil. If you have plants in containers, there needs to be enough water added to the container so that water drains out the bottom.
If the soil in the container has gone very dry, it tends to pull away from the sides. If this happens, you need to apply some water to the soil and then allow time for it to absorb that water. You should wait a few minutes and then apply some more water. You may need to do this multiple times until the soil has absorbed enough water to expand back to the sides of the container.
You will find that tomato plants grown in containers tend to outgrow the container unless it is large enough for the large root system that a mature tomato plant will possess. Many times in the spring, you will get a tomato plant in, say, a 1-gallon container, which is about an 8-inch pot. For a tomato plant to grow properly, it needs to be in a 5-gallon pot, which would be about 14 inches in diameter.
A while back, Dave from Newburyport emailed in a question about a tomato plant that wasn’t doing so well. I suspect that the plant was in too small of a container. At this point in the season, it’s hard to transplant any tomato plants into bigger containers without setting the plants back in their growth cycle. When planting into containers, keep in mind the ultimate size of the plant and use a large-enough container.