Agreed. Go for it, then.
And, y’all don’t think the “summer plum” color is too wintry/dark? Seems like a dumb question given the name of the color! Dark seems a bit more formal and mature to me than the brighter colors.
No.You know better what colors work for you. At the end of the day, though, nobody, other than perhaps DH, will be focusing on your dress at a wedding. 
IMO, the color is perfect for a 6 pm event. Not too dark, not too light.
Love it @Hoggirl! I like the plum color too. Navy would be my back up color. Lovely!
Very pretty dress. Macy’s has it in charcoal, turquoise, ice blue, and summer plum with most sizes available. I may order it for my daughter’s shower.
Love that Dillard’s dress and the blue color! It looks perfect to me with the right accessories and wrap, just to keep off the A/C chill.
I agree that the dress from Dillard’s would be very appropriate for such an event. Personally, I don’t like black at weddings. There are so many other nice colors and black looks good, but why wear it at a wedding?
I would just suggest that before getting a solid color dress, that you find out the bride’s colors. I once went to an outdoor wedding in Columbus Ohio in the summer and bought a lovely purple bandage dress. It turned out to be exactly the same shade as the bridesmaids’ dresses, and they wore three different styles. I know the photographer was trying to figure out how I fit into the bridal party, but of course I was just a guest. I was embarrassed but what could I do?! Too hot to leave on my shawl.
^that is sound advice @Marilyn. I kinda feel sorry for my friend, the MOG. She really seems to be have placed in the “wear beige and keep your mouth shut camp.” I’m not sure how in-the-loop she is being kept on anything related to the wedding. 
I can ask her, but I’m not sure she will know!
That dress would be fine, in my opinion. Nice earrings, and you are good to go. Make sure you have a wrap…because while it will be sweltering outside, it will be very chilly inside.
I can’t imagine any part of this will be happening outdoors. Since these are close friends, maybe ask…but i would seriously doubt it.
It’s formal not black tie, so suit is fine. Wedding party might be in tuxes. If the wedding is indoors I would probably freeze - I’ve never met air-conditioning that wasn’t too cold. I hate shawls. I have a dark blue halter top velvet dress that I have worn to summer formal dances that I love.
I like that dress you posted Hoggirl, in fact I like it best in plum.
“Make sure you have a wrap…because while it will be sweltering outside, it will be very chilly inside.” Great advice, @thumper1. I have shivered at many air-conditioned restaurants/parties held in sweltering locales.
I agree that if it’s inside at a hotel there is a high likelihood of you being miserably cold if you dress for the weather outside. Did that once on a 94 degree day. Never again!
So, what color of a wrap with the plum dress???
Silver?
I have a black cashmere wrap and a cream color one (thank you for,the suggestion years ago @bunsenburner).
I think either would work with your dress.
Both silver and gold would work just fine with this dress!
Love the dress you selected, @Hoggirl! And I agree that both silver and gold would look nice for shoes, a wrap, etc.
I ordered the dress today. I am going to exams the “bling” at the waistline to determine the best “metal” to go with for shoes, etc. I saw a wrap at Nordstrom’s that is a silk and cashmere blend. There is one that is a light silvery gray.