Average temperature is defined as the daily average air temperatures at ground level, averaged over an entire year. Average temperatures are rising in New York State:

• Historical observations: Since 1901, average temperatures in New York State have increased by almost 2.6°F. Temperatures since 2000 have been higher than in any period in recorded history. New York has warmed more quickly than the U.S. average.
• Projections for the future: Average temperatures are projected to increase in all regions of the state. Temperatures are projected to rise between about 5°F and 11°F by the end of the century.

Warmer temperatures contribute to conditions that allow invasive species and pests to spread, increase drought risk, and stress animal species that need a colder climate. Higher temperatures also generally lead to longer growing seasons and could increase yields for certain crops.

New York State experiences distinct seasons, with cold winters and warm summers. Seasonal temperatures—or average temperatures over an entire season (spring, summer, fall, or winter)—are increasing statewide:

• Historical observations: Winter is warming faster than other seasons in New York State. This winter warming means less snow for many parts of the state.
• Projections for the future: All four seasons are projected to continue warming across all regions of the state. The northern parts of the state are expected to see the largest changes, especially in winter. Winter temperatures are projected to increase between 3.9°F and 8.2°F by the middle of the century and between 5.5°F and 12.5°F by the end of the century.

Seasonal patterns are important for daily life, as well as for New York’s economy and ecosystems. For instance, agriculture depends on seasonal timing for planting and harvesting. Warmer winter and early-spring temperatures are leading to changes in thaw and frost patterns that threaten some crops. Warmer winters and less snow also threaten winter recreation, a key source of jobs in many parts of the state such as the Adirondacks, Catskills, Central/Finger Lakes, and Great Lakes regions.

What is considered extreme heat varies from one part of the state to another. For this assessment, a “heat wave” is defined as three or more days in a row with maximum temperatures at or above 90°F. Although New York State already experiences some very hot days, evidence shows that extremely hot days are happening more often:

• Historical observations: Days over 90°F occur somewhat regularly in New York City but are fairly uncommon in northern parts of the state. Metropolitan areas tend to be more affected by heat, as areas with a lot of buildings and pavement and fewer green spaces become “heat islands” that retain and intensify heat. A U.S. Environmental Protection Agency analysis found that heat waves became more frequent in the metropolitan areas of Albany and Buffalo from 1961 to 2021.
• Projections for the future: Days above 90°F and days above 95°F are projected to become more common across all regions of New York. Multiday heat waves are expected to occur more often and last longer in the decades ahead.

Extreme heat poses risks to people’s health, as well as wildlife, infrastructure, and parts of the economy. Extreme heat is especially dangerous when it lasts for several days. In the United States, extreme heat causes more deaths than any other type of extreme weather. Heat waves affect all New Yorkers, but especially low-income households with less access to air conditioning, outdoor workers, older adults, children, unhoused people, and people with medical conditions.

Higher heat indexes—and more days with high heat indexes—lead to more risks to human health from heat, such as heat exhaustion or heat stroke.

Like extremely hot days, very cold days occur as a natural part of day-to-day variation in weather. Extremely cold weather poses health risks for people who are unprepared and exposed, and it can also damage infrastructure. However, some cold weather is also part of New York’s seasonal patterns. Extremely cold days are becoming less common in New York State:

• Historical observations: Temperatures that are considered “extreme cold” vary based on regional climate. Temperatures below 0°F are common during winter in some regions of the state. They are rare in others, like New York City. Winter nights are becoming warmer across the state, as temperatures below zero have occurred less often since 1990.
• Projections for the future: The number of days per year with temperatures below 0°F are projected to decrease across the state. The number of days per year below freezing (32°F) are also projected to decrease. At Lake Placid, only 2 to 11 days per year with temperatures below 0°F are expected by the end of this century. This is a large decrease from the 33 days per year that occurred from 1981 to 2010. New York City is projected to have 31 to 61 fewer days below 32°F per year by the end of the century.

Having fewer days below freezing can have many impacts. For example, ticks that carry Lyme disease can more easily survive the winter and spread across the state. Cold weather is crucial for recreational activities that involve snow. Warmer winters are projected to lead to longer growing seasons, which benefit some crops, but pose risks to others as seasonal patterns change and some pests increase.

Changes in the temperature outside affect how much energy New Yorkers use to heat and cool their homes and other buildings. “Heating degree days” and “cooling degree days” measure this effect. They take each day’s daily average temperature and calculate how far it is below or above a common reference point of 65°F. Heating degree days are used to estimate energy requirements for heating. Cooling degree days are used to estimate energy requirements for air conditioning. Both heating degree and cooling degree days are changing statewide:

• Historical observations: New York State experiences substantially more heating degree days than cooling degree days each year. Annual average temperatures are well below 65°F throughout the state. However, from 1895 to 2022, heating degree days decreased by about eight days per year, and cooling degree days increased by about two days per year. Much of the change has happened in the past two decades.
• Projections for the future: Heating degree days are projected to continue to decrease across New York State. Cooling degree days are projected to increase.

Changes in heating and cooling degree days could mean that New Yorkers use less energy for heating but more energy for air conditioning. Not all New Yorkers have access to air conditioning. As the number of cooling degree days increases, people without air conditioning are especially at risk from high temperatures.