The Center for Climatic Research has been involved in the development of a number of heat/health warning systems over the past several years. These systems are based on the following premises:

1. Humans respond to weather in relative, rather than absolute, fashion. 2. Different systems are necessary for each urban locale because of unique meteorological and demographic character. 3. Systems should be tied into real human heat/health responses rather than arbitrary meteorological threshold values. 4. A synoptic climatological methodology is very efficient in such systems because it can identify "oppressive" air masses associated with deteriorating human health.

The goal of this presentation is to describe the development of our heat/health systems and to discuss how they are being utilized in numerous locales around the world.

The following steps are necessary in system development: 1. Determine historical mortality/weather relationships using a synoptic approach (identify the oppressive air mass). 2. Develop a means to identify those weather conditions within that air mass that lead to significant increases in mortality. 3. Develop a means to forecast, over the next 48 hours, those weather conditions that lead to mortality increases. This will involve the forecasting of days within the oppressive air mass. 4. Develop a set of intervention plans so the city can mitigate health damage during dangerous weather. 5. Once system is operating, develop a method to check its effectiveness in terms of saving lives.

The systems are housed on a password-protected website available to the responsible public officials. They estimate the numbers of deaths expected over the next 48 hours from heat-related causes and allow ample time for the responsible agencies to put intervention plans into place.