Studies have found that people with lung disease are particularly susceptible to heat-related death. High temperatures and wider temperature ranges may also trigger asthma attacks. We will examine acute effects of temperature and temperature range on lung function, and the role of temperature in modifying respiratory effects of exposure to air pollutants. Air pollution exposure is associated with lower lung function. This study will test if these effects are different if the previous day was extremely cold or hot. This project will also assess if people with asthma or COPD are more susceptible to respiratory effects of temperature. The findings could lead to more precise warnings about air pollution and temperature for people with lung disease.