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As with all things, our health is influenced by climate; temperature, humidity, and even atmospheric pressure can effect how we feel.

Turning up the heat

Global climate models suggest that over the next 50 years, southern Ontario is likely to experience more frequent, more intense, and longer heat waves. An increase in the number of hot days (over 35°C) could increase the risk of heat-stress-related health problems, especially in the very old, the very young, and those with chronic lung diseases such as asthma.

Right now in southern Ontario, the average number of days over 35°C is 10 per year. This may increase to as many as 46 per year by the middle of the next century. The urban heat island effect will exacerbate this situation in many of our cities.

(modified from Oke, 1976)

(modified from Oke, 1976)

The urban heat island effect occurs when natural vegetation is replaced by surfaces that absorb heat, such as building roofs and walls, and pavement. This can make cities several degrees warmer than nearby rural areas.

A warmer climate and longer frost-free seasons may permit the spread of new diseases from warmer climates, such as Lyme disease, malaria, and West Nile virus.

Number of hours with ozone over 82 parts per billion

One of the highest concentrations of smog in Canada is in the Windsor to Québec corridor. Permanent lung damage can occur in healthy adults who spend four hours in air with ozone levels of 82 ppb (parts per billion).

(Environment Canada)

(Environment Canada)

Bad air days

Since the creation of smog depends on a mix of urban pollutants, temperature, and solar radiation, warmer daytime temperatures will likely increase the frequency and extent of smog problems in our cities.

Did you know?
Winter and summer temperature extremes are responsible for more deaths than are more violent weather events such as tornadoes, blizzards, or floods.

(NRCanada photolibrary)

(NRCanada photolibrary)

Did you know?
One third of the carbon dioxide emissions generated by human activities comes from transportation. Furthermore, in urban areas, vehicles produce up to three quarters of the pollutants that combine to form ground-level ozone, the main ingredient of smog.


Auld, H., MacIver, D., and Taylor, M., 1999: Climate change and the conservation challenge; Environment Canada.

Oke, T.R., 1976: Inadvertent modification of the city atmosphere and the prospects for planned urban climates; in Proceedings, Symposium on Meteorology Related to Urban and Regional Land-Use Planning, Asheville, North Carolina; World Meteorological Organization, Geneva, Switzerland, p. 151-175.

Our health