Watering today, I sighted the first squash at the Tower.
Considering the size, I don't know why I didn't see it before. I hope that this indicates the last few days have been prime growing weather, and not that I'm going blind.
(An alternative explanation is that, at last night's Sustainable Belltown meeting included informal tours of the plantings at the Tower; it's possible the squash was teased out for better growing.)
UPDATE: my wife gently pointed out that it's a cucumber, not a squash.