That looks like it could be a cultivar of Geranium sanguineum (Bloody crane's-bill or Bloody geranium) or something closely related.
Image source: Keith Weller, USDA Agricultural Research Service, Bugwood.org — CCA3.0.
Some features that are consistent with this id are: the five identical bilobed petals, flower size and shape, hairy stems, and leaf form (palmate with five lobes each with three large 'teeth'). The flower features I can distinguish rule out related genera such as Pelargonium and Erodium, which have flowers that are not radially symmetrical. If this is a Geranium, then there should be 10 free stamens and the stigma should have a style with 5 branches.
This species is cultivated and typically blooms from June to August, which fits your described location and time.