With temps this high, plants are impacted. They may begin to shut down to conserve water & may look like they are wilting. Or they may just die without a good soaking, due to the heat stress. Vegetables need about 1 to 1 1/2 inches of water a week while fruiting. The best way to water tomatoes planted in the ground is with a soaker hose so you get the water delivered slowly & around the roots. Regardless your plants will not produce as well during periods of very hot temps. For example, my tomatoes have cracks in them now, which is not aesthetically pleasing to the eye, but does not impact the taste. I regularly sell produce at the local Hermann Farmers' Market & have created a slogan because of these conditions. My new slogan is, " We specialize in the ugly tomatoe." And when we get hot temps, with alot of rain, then back to hot temps, tomatoe end blossom rot is more likely to occur.
Be sure to maximize your watering of your plants by water frequently (1-2 times per week, assuming we don't get any significant rainfall) & giving your plants a good, long term watering session so that the water has an opportunity to make its way to the roots & surrounding areas. Minimal watering only encourages shallow root development.
If you have fruit trees, now is also the perfect time to break out those 5 gal buckets that always seem to get holes in them. Or drill about 5-6 holes in the bottom of a bucket & then set them near the base of your trees. Fill the buckets up & let them gradually empty through the bucket's holes. Be sure to run your water source until the water's temp is not hot. One does not want to accidentally use hot water on any plants. Putting hot water from hoses left in the sun will damage the roots of anything. In fact, you can use hot, boiling water as a natural, non-chemical way to kill many undesirable plants. Just pour this hot water onto any plant you want to get rid of, ensuring the hot water gets to the plant's root system.
Also, if you have planted crops close together (which I highly recommend), you will have less soil exposed to the sun. The shade between the plants will reduce the amount of sun on the ground's surface, not only discouraging weed growth, but keeping the evaporation of water to a minimum. Placing straw between the plants will also discourage weed growth & water evaporation, while adding organic matter to your soil.
Hopefully at this point in the season, you have your garden well underway & are reaping the benefits of earlier plantings. However it is not too soon to start thinking about what fall crops you will plant. The first frost date for our area in MO is around the 3rd week of October. So many crops will have ample time to produce prior to this date. Always something to do in a garden!
Stay cool, hydrate you & your garden & enjoy those homegrown fixin's!!