B737 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 112.43; Flight Crew Total 7372.22; Flight Crew Type 7372.22
Situational Awareness
Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
Flight Crew Overrode Automation
Chart Or Publication; Procedure; Human Factors
Intended to land flaps 30 in windy conditions with add speed of 14 knots.  Visual approach on Visual Approach Slope indicator and slightly below ILS glide slope. We received a Ground Proximity Warning alert for 'too low terrain'. Rechecked landing gear was down and landed. We realized on very short final that flaps were actually set to 25 instead of 30. We did not select flaps to 30 since we were so low. With the extra speed we had added for the gusty winds; I felt we were safer to leave them set at 25 and land.
While on final approach  we experienced a Ground Proximity Warning 'Too Low Terrain' aural warnings. Knowing that we were on glide slope and Precision Approach Path Indicator and the runway was in sight in VFR conditions; we decided to continue the landing. We ensured that the landing gear was down and that we were free of terrain; however; on short final the Captain noticed we were at flaps 25 instead of 30. It was decided to safely complete the landing since we were stable on speed and path. We already had built in a 14 knot wind additive for the windy conditions. The entire approach was stable including at the 500 foot 'Stable' call out point. I take responsibility for misreading the flap gauge; and will certainly give it more focus in the future. One potential factor; not an excuse; is there was the distraction of balloons going by our aircraft around the time of the landing checklist. I reported the balloons to Tampa Tower.
B737 flight crew conducting a Visual Approach reported the flaps were set incorrectly resulting in a Ground Proximity Alert on short final.