This is the month that matters. The average CPI-W for July, August and September compared with the same months for 2017 is what determines the 2019 COLA.
The July CPI-W was 246.155 Compare this with the 2017 three month average of 239.668
Of the CPI-W for August and September is at least 256.155, the 2019 COLA will be 2.9%. Still a chance for 3%.