Water early enough in the day that the foliage has a chance to dry.

I usually water in the morning because we get quite a breeze by 9:30 AM.

That old saw about not watering in the middle of the day came about because someone conceived of the idea that the water droplets would act as magnifying lense and burn your plants foliage. No research gas ever shown that to happen. While it is probably best to water in the morning so your plants foliage can dry out before nightfall, watering mid day will help keep the plants cooler which is also beneficial to them, especially on a really hot day.

anytime but dusk .. mildews on certain plants are caused/exacerbated by sitting water on the leaves and muggy nights ....

mid day would not be best just on the amount of water which is lost to evaporation .... instead of given to the plant ...

ergo.. morning is suggested as the best .... ken

Never water in late afternoon,all follage must be dry going into night fall. But as you and me like the spray of water in the summer heat,so do our plants. I through out ath summer always give my plants a mist spray. :)

Nighttime is definitely out, unless you have a soaker system that puts the water into the ground, not on the plants. I have several beds that do use soaker hoses but I still water in the early a.m. The others I have little rosebud sprinklers, again no spray on the plants. The one exception is when we have had long, hot dry spells. Then I will use the oscillating sprinkler to "dust off" the plants to help them breathe better.

The admonition of "never water at night" or "plant foliage must be dry going into the night" can be refuted by the simple fact that it rains in the evening and during the night, and plant foliage does not suffer harm from that rain. I have never seen a good explanation of why that happens from anyone.

I've never paid any attention to the time of day when watering and truly feel that the most important issue is that watering should be done when the water will do the most good. I live in northern Alabama, where we are in the midst of a harsh and frightening drought. We've been doing most of our watering in the evening hours (even after dark), when the air is a bit more humid, the soil is cooler, and the water will have a chance to stay IN the soil longer...doing some good for the plants.

Lol, I also give some areas of the gardens a shower in the daytime, too. But that is strictly for the birds and the insects.

The most compelling reason to avoid watering in the evening is that it extends the dew period and this "indifference" can lead to disease.
For example if dew starts at 9.00pm and extends until 4.00am, the grass blades might remain wet for 8 hours until the sun dries out things. During this time the temperature might be favorable for a fungus to develop for only an hour or two. (Up to say, 11.00pm. and not long enough to manifest disease.) However if I watered that lawn after sundown, there can be up to 4 hours of wet leaves and favorable (for fungus) temperature before it starts dewing. In short, the grass blades can remain wet all night and somewhere in there the temperature will be favorable long enough for disease to be manifested.

What tiem in mornding should we water? Before Sunrise? During Sunrise? After Sunrise? The morning is many hours here in Michigan.

It doesn't really matter, though watering when the plants and soil is still cool is optimum.

My explanation and reasoning for stating that the best time to water tomatoes or any plant is when the plant needs it. That is usually during the hottest time of the day. Traditional thinking on this would claim the opposite. It is a widely held believe that water droplets on a plant burns the plant. This is incorrect. As water evaporates, it cools the plant and surrounding area. It removes energy in the form of heat. Traditional reasoning is based only on a small portion of the everything involved. In applying the laws of physics, the same amount of water evaporates in a 24 hour period regardless of the time when the water was added. The plant is more efficient at converting the energy from the sun when that plant is not stressed from heat or dehydration. The result is better ground coverage and less wasted water from the soil being heated. Remember the leaves soak in the Suns rays and convert this energy into plant growth. The plant will be cool to the touch. The ground will be hot.