Interest in climatologically based indices to the economy and human health has been growing among applied climatologists during the last decade. Strong relationships have been found between seasonal weather and the buildup, persistence, and transport of hazardous ground-level ozone concentrations. The growing interest in climatological indexing, together with the potential for its application to air quality aspects of human health and the economy, has prompted pilot research into the feasibility of a climatologically based index to seasonal exposure to harmful ozone concentrations. Climatological indices of this sort recently developed typically extend over a time scale of many decades and a spatial scale of either the whole USA or a region within.

Annual counts of days exceeding the new USA EPA threshold of 80 ppbv eight-hour mean ozone concentration are related to (multi-)monthly average temperature within the period April-to-September, using temperature and ozone data covering the period 1986 through 1995. Such a relationship is developed for the vicinity of each of 23 climate divisions in the Northeast USA categorized as metropolitan by a statistical analysis of total population and population density, and the relationships are aggregated to the regional level by population weighting.

Median Pearson correlation of ozone exceedance counts to seasonal mean temperatures within divisions is 0.81, comparable to that underlying similar indices, suggesting a temperature-index approach to modeling seasonal high-ozone exposure potential may be useful within a largely homogeneous climate region. Further study is planned using diurnal temperature range and for other USA climat e regions.