I noticed it happen, then asked around and at least 1-2 people said they saw the same thing.
Others seem not to have this problem because they keep harvesting tomatoes right up to frost. Maybe where they live, the first frost occurs soon after nights go below 50 - I guess that would mean a warm summer and/or short fall.
My summer nights very often go below 60, and might dip down another 10 degrees whimsically early.
