Hat tip to Jenn, whose photo has me thinking this is a mirid plant bug, Dicyphus famelicus, family Miridae (with usual, I am not an expert, maybe not this species, etc. dislaimer). The short, sharp proboscis combined with the proportionately slender body had me thinking it was some sort of mini-assassin bug (family Reduviidae), but assassin bugs have a certain squirrelly appearance around the head — something about narrowness and position and size of the eyes — a squirreliness this bug did not possess. Plant bugs are pretty varied as a group, but I typically associate them with angled back end and wider bodies as opposed to this slender and flat-backed bug. But so it goes.
BugGuide.net tells us that eggs are laid in spring, and adults die off by late June, giving way to nymphs in July. This adult, shot in early June, looks like a fertile female which puts it off the timeline a bit, but BugGuide was citing a Canadian-based reference, and our bug neighbors to the North usually have to get stuff done earlier to beat the cold weather. It’s just a stroll in the park down here in New England (albeit a stroll at a temperature in the teens at the time of this writing).