Hey,
Ive been looking in older posts but havent been able to find answers. Im wondering if anyone has has experience traveling in cambodia during july/aug? Is it still possible to sunbathe and go swimming or does it rain/storm up all day in generall?
Im a female and traveling alone for 3 weeks. Ive never been there before, so im thinking about safety.. Any inputs?

Does not usually rain all day so no problem sunbathing or swimming - most likely (very) heavy storm in afternoon or early evening lasting round an hour
Safety basically take normal precautions although if you intend being in Sianoukville then best to take more care at night as there have been incidents (and not just aimed at females)
As bigal1 said. I find Cambodia particularly pretty during July and August as the countryside can be lush and green with growing rice paddies, also the daily rainy spells tend to keep the dust down which tends to coat everything in dry season. Enjoy.
may keep the dust down but can results in very dirty feet as paths and roads quickly flood if you are in the country

Normally the weather is ok at this time of year. This year, at least in Sihanoukville, we have just had a month of pretty bad weather ( what is normally expected in September/October) however it looks sort of ok for the next few weeks. As for the stereotypical Sihanoukville knockers, ignore them - take the normal precautions you would take any where and you will probably be safer here then any other large town in the world and that includes any other large town in Cambodia.
Not much rain in Siem Reap at the moment, limited to a few hard, short showers.
Quite a few thefts here of late, hundreds of thousands of Khmer workers coming back from Thailand does not help.
However, crime against foreigners is rarely violent and consists more of bag snatching and breaking and entering.