Scientists have warned that floods, droughts, storms and rising seas will encourage diseases such as malaria, dengue and cholera, as well as heat sickness, homelessness and hunger.
The new unit set up by the World Meteorological Organization (WMO) and World Heath Organization (WHO) will pool expertise to advise on health perils posed by shifts in the weather.
"Climate change is leading to an increase in extreme events such as heatwaves and heavy rains, which have a major impact on human health," WMO Secretary General Michel Jarraud said in a statement.
"We need to have a common understanding of the challenges we face in order to overcome them."
WMO spokeswoman Clare Nullis told reporters there had been growing demands from the health sector for "reliable" weather and climate advice.
Climate-smart health systems can save numerous lives and greatly improve the efficiency of services, the agencies said.
They pointed to dust forecasts in the Sahel to help vaccination drives against meningitis -- linked by scientists to wind and dust levels -- and seasonal forecasts of rainfall to help malaria control campaigns in the tropics.
The new office will start with a programme to help Malawi and Tanzania incorporate weather and climate information into their health planning.
Flavia Bustreo, WHO's assistant director-general in charge of family, women and children's health, said weather often had insidious impacts on well-being.
They "often occur indirectly and more slowly, such as under-nutrition resulting from crop failure, respiratory diseases from poor air quality, and water-borne and vector-borne diseases," she said.