Prenolepis imparis should be flying all this and next month (April) but only on warm days above 60F or so. Flights usually start after noon at the earliest but are more likely to be seen closer to 4pm -5pm and last until sundown. It's best to find a colony or two of these ants and observe them at this time of day when the temperature feels right. On days when they fly it's usually warm enough that you don't need a coat but wind doesn't matter for this ant. They are a very ill-weathered ant. They'll fly in cloudy conditions with wind gusts up to 70mph.
Swarms gather around trees and are usually low to the ground, sometimes above the canapy but not often. Males tend to greatly outnumber the queens too so swarms can appear as swarms of gnats. They don't fly as dynamicaly as gnats though so walking through a swarm will result in several of them landing on you, where as gnats will likely fly away more easily. Knowing what male ants look like is also handy.
As you can see from the photo, queens are birghtly colored and in my opinion one of the prettiest ants you can find. There's something about the blushing red orange color of the thorax, and the blond yellows of the abdomen. As far as I know this is a unique color combination in the ants world.
Workers are about 4 milimeters long. Their color is either a pale brown color or a dark almost black color. This ant is also found all over America but are most common in forested areas.
Happy Anting