I would disagree with Skinny and say bring arm warmers.
I would bring:
Bib shorts x 2
short sleeve Jersey x 2
Super lightweight summer baselayer x 2
A gilet that packs down really small
Pair of arm warmers
Pair of light weight leg warmers
A decent waterproof jacket, that you can wear on and off the bike
I would disagree with Skinny and say bring arm warmers.
I would bring:
Bib shorts x 2
short sleeve Jersey x 2
Super lightweight summer baselayer x 2
A gilet that packs down really small
Pair of arm warmers
Pair of light weight leg warmers
A decent waterproof jacket, that you can wear on and off the bike