Putting all these factors together for August reveals the periods of greatest vulnerability to major storms with high winds and heavy precipitation – and the flooding that often accompanies the latter. These are also times when there’s an enhanced risk of moderate to severe seismic activity, including Magnitude 5 and up earthquakes, as well as volcanic eruptions. August 1-10 is the first and longest of these, from the lunar north declination peak on the 2nd through the new moon on the 6th and southward declination crossing on the 9th. This is followed by a brief shock window (August 15-17, centering on the Moon’s south declination peak on the 16th). A longer one is connected with the lunar perigee on the 19th and the full moon on the 21st, stretching from the 18th through the 24th. And last comes August 28-31, under the aegis of the Moon’s north declination peak on the 29th. In particular, greatest vulnerability tends to come within a day or two of the exact dates in these several cycles – e.g. the 6th and 18th.
http://www.astropro.com/forecast/predict/2013-08.html