As well as telling parents when their baby's room is the correct temperature, they will also display messages about fire safety and smoke-free homes.
Specialist midwives from Barnsley Hospital's stop smoking maternity service will give practical advice and support to smokers.
The thermometers have been funded by the fire service, with the project being awarded about £6,000 through South Yorkshire fire authority's community reserve fund.
They are being handed out by Barnsley Maternity Unit.
Joanne Poskitt, specialist midwife in drug and alcohol use, said there were strong links between smoking homes and sudden infant death or meningitis.
"The new thermometers are a practical and simple tool which will help parents provide a safe sleeping environment for baby. We have already started handing out the thermometers and all new parents-to-be will be given a thermometer at their first antenatal appointment."
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