Wear Vietnamese áo dài if you have one, can, or want to! It's otherwise semi-formal.
It will, however, rain earlier in the morning and might get "evening rain" chilly that afternoon/evening (think mid-high 60's F). If you run cold, something to keep in mind since the event is outside in my father's garden (there will be tent canopy, however). We'd rather folx prioritize warmth & comfort!
At the end of the day, y'all should wear whatever you feel comfortable and beautiful in. We'd love you in jeans!
Even if it stops raining by the time the event starts, the ground will probably be wet and muddy so wear appropriate shoes!
Coats & any extra layers you bring can be stored upstairs in bedrooms.
Wear Desi clothing if you have any, can, or want to! It's otherwise formal. Femme clothing usually consists of saris, lehengas, & salwar kameezes. Masculine clothing tends to be kurtas or Western suits.
If planning to wear Western wear and wanting to fit the vibe, keep in mind that Indian wedding guest attire tends to be more formal and ornate.
Rain shouldn't be a huge problem on Saturday since all events will be held indoors. Note that coat racks at the venue are not available (only a few coat hangers), so will have to be held onto by you. And consider bringing umbrellas for when you have to walk from the parking lot to the venue (although they ARE located on the same street right across from each other).
At the end of the day, y'all should wear whatever you feel comfortable and beautiful in. We'd love you in jeans!
In both of our cultures, the color red is usually reserved for those getting married and the color white is the colour of mourning and death.