Japanese HII rocket: Seasonal launch limitations?

According to this page,

  1. Is it true that the H-II launch vehicle has seasonally-restricted launch windows?

  2. If so, what are the acceptable launch periods in the year?

  3. What is the cause of these limitations, if any?

I’ve looked around a bit, but JAXA’s website and several others don’t seem to give a reference to this purported phenomenon.