Bow Market in Somerville's Union Square, of course, as Ron Newman shows us, in a photo he took around 4 p.m.
That's when lots of other folks looked up and also spotted rainbows. John McMahon captured the double rainbow over Cambridge's Huron Village:
Not everybody saw double, but some of the rainbows really showed off the full ROY G. BIV effect, like this one over Jamaica Pond:
Swirlygrrl forwarded this view from Somerville's Winter Hill: