GA flight instructor reported ATC issued altitude alert for unknown reason.

Attributes
ACN	1554097
Time
Date	201806
Local Time Of Day	0601-1200
Place
Locale Reference	LOU.Airport
State Reference	KY
Environment
Light	Daylight
Aircraft 1
Make Model Name	Small Aircraft High Wing 1 Eng Fixed Gear
Operating Under FAR Part	Part 91
Flight Phase	Final Approach
Route In Use	Direct
Flight Plan	IFR
Person 1
Function	Instructor Pilot Not Flying
Qualification	Flight Crew Multiengine Flight Crew Instrument Flight Crew Flight Instructor Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 200 Flight Crew Total 13000 Flight Crew Type 1000
Events
Anomaly	ATC Issue All Types Inflight Event / Encounter CFTT / CFIT

Narrative:

While executing RNAV 24 klou approach with a student; we received a low altitude alert from tower on final segment of the approach. I verified current altitude against the approach chart; and the altimeter setting. I did not observe any discrepancy. I informed the tower that we had just reached VMC below the cloud bases; and that we were at 1;200 feet MSL. Provided a PIREP for cloud bases. Continued the approach to an uneventful landing.

Original NASA ASRS Text

Title: GA flight instructor reported ATC issued altitude alert for unknown reason.

Narrative: While executing RNAV 24 KLOU approach with a student; we received a low altitude alert from tower on final segment of the approach. I verified current altitude against the approach chart; and the altimeter setting. I did not observe any discrepancy. I informed the tower that we had just reached VMC below the cloud bases; and that we were at 1;200 feet MSL. Provided a PIREP for cloud bases. Continued the approach to an uneventful landing.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.