My greatest watering challenge is understanding how fast the ground or cotainer soil dries out even in the high humidity! In Arizona container vegetables get watered, every day, or the container will feel like it weighs ounces - bone dry.
Yep, low humidity and high temps literally suck the moisture out of the soil. There is no fast rule as to how often to water as everyones soil and conditions are different. Just remember that there is no such thing as too much water but there is such a thing as water too often. I have tried different moisture meters but no two of them will show the same thing so I just use the old standard measuring tool, my finger. And you should keep in mind just where the roots of your plants are. Depending on the plant, most plants roots are fairly deep, probably around 4-6 inches deep so if the soil is dry at 2 inches at 6 inches it is still moist. So, to make your plants roots go deeper in search of moisture and nutrients, every so often let the top of the soil dry to 3 inches. It just takes a lot of trial and error to know when to water but it is better to water less often than more often in most cases.
Containers are another problem for many gardeners. Containers are mostly made of plastic or clay and some of the plastic containers look just like clay containers. You have to water more often in a clay container than in a plastic container because water evaporates through the sides of a clay pot plus the top but the amount of water you use at one time stays the same. Complete saturation of all the soil whether it be plastic, clay or in the ground.
Then there are the people who water a little every day. They think that watering enough to keep the plant from wilting is enough water. They go out and water their lawn or tomato plant enough to get the soil on top muddy and think that is plenty, It's not. Enough water should be put down to make it muddy at least 6 inches deep. They always say that watering deep is a waste of water, that there is nothing there to water, no roots no nothing so why bother. The reason to water is because you want roots to be there. Deep strong roots enable the plants to produce more and in the case of lawn grass make the grass much healthier and thicker. It is a fact that a deeply and correctly watered lawn actually uses about the same amount of water but the end product is much better and less expensive than an incorrectly watered lawn. Well, that's my rant about watering today