Hello,
I am hoping to travel to Vietnam in late June. However, people are warning me about the rains. Will this significantly decrease the quality of our vacation? I have spent summers in Japan, so I know that in humid climates, it can rain for an hour, then clear up, and life goes on. Is it worse than this in June/ early July in Vietnam? As a tourist will I be stuck in my hotel room all day?

Vietnam is affected by different monsoons in different areas. Take a look at www.weatherbase.com and check each city you would like to visit.

never predict the weather during rainy season! Even the statistics dont help much. If you are lucky it drizzles just an hour or so in the afternoon.
If you arent, it pours for a week or more in a row.
Just try it out.
Good luck!

Yeah, it's hard to predict the weather in advance. You're right that it might rain for some continuous days but it often rains few hours in the late afternoon, then stops. I think in late June, it doesn't rain much as in July. Check the weather carefully before your trip!

it's not rain too much, but quite hot in June in the North of Vietnam, because it's summer