Mike,
I've lived in VA/WV for nearly 40 years. Most years -- depends on tropical storms and hurricanes, but mid-July through early September usually have the lowest water levels in ponds, streams, and rivers.
Here is a link to average rainfall over a 30 year period of time.
30 Year Average Rainfall for Cities in US Monthly average rainfall stays pretty consistent year around in Virginia, at 3-4 inches per month, but there there are major differences in what happens with that water during different times of the year. The rains in July through early September are more typically from thunderstorm activity instead of two to three day light rain/snow at other times of the year.
I tried to find historical average river flow charts from USGS, but I don't know where they went. But, in years gone by, I've looked at them closely, and it is very interesting to see how much the flow rate drops in rivers like the James, the Rappahannock, the Shenandoah, etc., during July, August and September. There will be two or three day spikes from thunderstorms, but in general they are down considerably from other times of the year.
Regards,
Ken
