In August, the Strange Horizons fiction department received 467 valid submissions, making August the 8th-highest-volume month ever. That's an average of 15 stories a day, down from the nearly 16 per day in July.
No days or weeks in August made the top-20 highest-volume days or highest-volume weeks lists. That's pretty unusual for recent months.
Comparison to recent years: August of 2008 saw 426 subs (a bit under 14/day). August of 2007 got only 361 subs (under 12/day). So submission volume has gone up by about 30% over the past two years.