brother,,, all clear in sept... no issues but my personal remarks abt this lake is... it is not a lake (in terms of size )... and trekking long hours for only this is not worth it... horse ride to make a milestone is another issue.. though ansu lake is not a milestone as well. i visited only once and i was disappointed....
better to go dudipatsar,, one of most rewarding and fascinating lakes....
anyways, if u wish to go to ansu,,, there is certainly no problem in september