I believe your answer is the year 2020
Northern hemisphere, south eastern part of the country
The term bioinvasion means that a plant or animal is not native in their current location and often spreads to a dangerous degree which is harmful to it's new environment, to the economy and to human health. An example of this is the Asian longhorned beetle which infected and damaged millions of acres of hardwood trees, as it was introduced in the United States.
For continental U.S. the answer is never. Since the earth's rotation axis is tilted 23.5 degrees with respect to its orbital motion around the su, one would have to be less than 23.5 degrees above or below the equator to have the sun pass direclty overhead
