after reading dozens of studies it goes like this:
summer = negative ions = favors girls
Fall= mix of ions with slightly more positive= slightly favors boys
Winter= positive ions = favors boys
Spring= mix of ions with slightly more negative ions= slightly favors girls
full moon= positive ions =favors boys,
a new moon = negative ions= favors girls
Also, if you live in a warmer climate the seasons will have less of effect. the seasons work with ions in two ways. First the distance of the sun (effects everyone) and second the temperature. Some people (like in Hawaii) the temps never get cold so this will have a less effect.
Also weather can change ions to. A cold front brings in more positive ions (but the storm before it has negative ions). A warm front more native ions.
A quick summery is all things nature has negative ions and all things powered have positive ions
More info on ions can be found in FAQ forum on ig.