has anyone travelled around vietnam in july and august. how was the weather ?

I've stayed in the south of Vietnam during that period. Yes that's the wet season and I had a lot of rain, pretty much every day in fact.
More positively though, it usually only rained for 1 or 2 hours in the afternoon. After the rain had stopped, the sun came out again and the place soon dried. You are best to plan your days around this as much as possible, but it can usually be done without too much trouble.

Central and Northern areas have a different climate. Unfortunately, I,ve not been to these areas during the summer months.

I travelled to Saigon and Nha Trang in early September and found that the weather did not hinder our enjoyment. It tends to rain late afternoon and in the evening and at night we say the most spectacular lightning.

In our second week we learnt to dive and the weather did not cancel any of our trips.

I think there were only 2 days out of our 14 that rained during the day and to be truthful, coming from England, it was not a hardship!