Northeast United States heat index climatology: 1981 – 2010

United States air temperature climatologies are widely available but few studies have addressed the heat index at climatological scales. Extreme heat is one of the most dangerous weather hazards and the impact of heat on human health is exacerbated when combined with high humidity. We therefore present a climatology of derived heat index values for New York and New England over the most recent climate normal period of 1981 to 2010. Results indicate that the average annual heat index value and the number of days with a heat index are highest at urban stations and decrease north. While the average annual heat index value varies little over southern portions of the region, the number of days with a heat index is significantly higher for large, urban areas. Trends indicate that changes have occurred in both the average annual heat index value and the number of days with a heat index but that these did not always change together.