Layer your daily outdoor clothing. T-shirt, sweater, jacket. I did ok with a fleece jacket, and not my winter parka. Based on your tours you may need to bring heavier clothing.
Bring rain gear, a poncho, umbrellas for sure.
When I was there last in early June and had alot of rain, cool, but, not freezing.
This year I am going late July, should be better, as with your dates.