I don't think it is still on the ATIS (too lazy to check), however what they mean seems pretty clear to me; there is a temperature inversion at an altitude of 3.800' of xx°., i.e. the temperature passing that altitude is by xx° higher than on the ground. This can be relevant especially during departure as you can expect a sudden 'loss' in thrust and/or speed.
The information given on the ATIS is a kind of 'heads up' by ATC.
Regards,
DBate