Did you notice that they went there in early July 2009, you will be going around mid August, it will be cooler than in July. Yes it will not be snowing, but hail storms are not so uncommon at altitudes over 10,000 feet in Kaghan valley and even a light shower will be freezing at that height. (Lake Saif ul Maluk is at 10,500 feet.) Just be prepared for something like it, carrying a raincoat should not be a burden, a two-piece rain suit is even better. Hiring horses help carry the extra stuff with you, even if you don't ride and the owner acts as a guide.
My recommendation, stay at Lake Saif ul Maluk at night and start early, if you hire guide/horse(s), then the earliest the guide/horse(s) are available. Otherwise, around 6:00 am(earlier would be better, if possible). I never went to Aansoo lake (personally I don't consider it a real lake and don't understand people's obsession for it) but I have heard quite a few stories of unsuccessful attempts (like talalarif2003's) and half as many of people just reaching the lake and returning after spending less than 20 minutes there.
