Our Micra has the manual HVAC controls rather than the automatic, but I would assume 16c was the lowest setting?
With my former Qashqai and Pulsar, and now Megane with 'digital' HVAC controls, as long as its not set to auto, 16 would be 'uncooled' air, but with auto enabled, it will slightly open the blend door to mix in some hot air until the cabin was at the set temperature, the fans will lower and it will try and maintain that set point by adjusting the blend door and fan speed.
Auto mode relies upon a temperature sensor to detect the cabin temperature to make adjustments. Sometimes they are not in an in an ideal position or maybe not calibrated exactly and either read too hot or too cool. 17c outside air temp is probably borderline
If you dont have auto switched on, It could also be that the blend door is not closing, either partially for fully.
Are you able to describe your symptom in a little more detail?
Are you running the HVAC with auto mode on or off?
If auto mode, what was your HVAC doing a couple of weeks ago when the outside air temp was in the 20's?
When you say warm air, is it luke warm, or does it eventually get hot if left long enough?
What happens if you increase the set point, does it pushed out hotter air?