Hi! I'm just up the road from you at the county line. Welcome!
It's true that the main nectar flow is over for us this year. I define "main" the same way as Joseph states above. In our area, that would start in March with the ornamental hollies, redbud, blackberry, tulip poplar, American holly, Tupelo, Linden and clover. Of course, other things are mixed with these, but these are the main indicator plants that start in late March and end in Mid May.
The Tupelo and Linden can be hit or miss, but I an fortunate to live close to some mature hardwood stands that do produce some years. I don't mention red maple because it's so early in the season there is rarely a large enough population of bees to bring in a surplus of nectar, though it is important for pollen and nectar for buildup.
There will be minor flows as long as rains continue into the Summer. The clover is reflowering right now, and the bees are working it due to the rain we have had. There will be some soybean and cotton in the area, and if the rains continue, they will provide a decent flow if you are close to a field.
The "dearth", meaning no nectar flow varies year to year here and is usually drought/ dry weather induced. It has started as early as May and as late as mid July some years. So far, we are looking good this year for a later, shorter dearth.
The Fall flow is variable here as well. It is all dependent on how much rain we have had through the mid to late Summer period. Mid Summer rains are needed to support the growth of the asters and goldenrods, while the late Summer to early Fall rains provide the extra mositure the plants need to produce nectar. Just because the goldenrod has flowers doesn't mean it is producing a nectar flow.
Hope this helps.