Executive Summary                 Introduction                 Letter

The Climate Challenge*

Nearly every environmental indicator in the 2023 annual report has a tie to the climate. The trend over more than sixty years suggests that Connecticut’s climate is getting warmer, and precipitation is increasing.

The state’s warming climate is evidenced by increasing annual average temperature, precipitation, annual cooling degree days (CDD) and growing degree days (GDD) and decreasing annual heating degree days (HDD).1

The trend for annual HDD is decreasing while the trends for annual CDD and GDD are increasing from 1961 to present. HDD for 2023 (5,015) was 16.2 percent less than the annual average since 1961, while CDD (931) and GDD (3,314) for 2023 were 13.7 and 8.3 percent greater, respectively, than the annual average since 1961.

Annual precipitation for 2023 (64.9”) was 41.6 percent greater than the annual average since 1960 (45.8”). The number of days in 2023 (20) with rainfall greater than one inch was 70 percent greater than the annual average (11.8) since 1960. It is predicted that as the climate warms, severe weather events, such as drought conditions and extreme rainfall, might become more frequent.2

Annual average temperature for 2023 (53.6 degrees Fahrenheit (°F)) was 6.1 percent greater than the annual average since 1960 (50.5°F) and the number of days greater than 90°F (12) was 21 percent less than the annual average (15.1) since 1960. For 2023, the average winter temperature was 20 percent higher than the previous 60-year average.


Technical Notes: *Weather data measured at Bradley International Airport (BDL). 


1 National Oceanic and Atmospheric Administration (NOAA), National Weather Service, Hartford-Bradley International Airport, Accessed January 4, 2024; w2.weather.gov/climate/xmacis.php?wfo=box.

2 Connecticut Department of Energy and Environmental Protection (DEEP), BUILDING A LOW CARBON FUTURE FOR CONNECTICUT ACHIEVING A 45% GHG REDUCTION BY 2030; portal.ct.gov/-/media/DEEP/climatechange/publications/BuildingaLowCarbonFutureforCTGC3Recommendationspdf.pdf#page=20.