Ohio’s midlatitude interior location and the lack of mountains to the north and south expose the state to incursions of very cold air masses from the Arctic in the winter and warm, humid air masses from the Gulf of America (formerly Gulf of Mexico) in the summer. Average summer high temperatures range from the upper 70s (°F) to the mid-80s across the state (1991–2020 averages). Typical winter low temperatures range from less than 20°F in northern regions to the mid-20s in southern areas. Lake Erie has a significant influence on the local climate, with nearshore locations being considerably warmer during the winter and cooler during the summer than locations farther away from the shores. Annual precipitation varies regionally, with the northwestern part of the state averaging around 35 inches and the southeastern regions averaging around 45 inches. Lake-effect snow, caused by the warming and moistening of Arctic air masses over the Great Lakes, is a hazard along the southeastern shoreline of Lake Erie, with some locations receiving over 100 inches of snow per year. Snowfall generally varies across the state, with northern regions receiving 60 inches or more annually and southwestern areas receiving less than 12 inches annually.
Time series of observed and projected temperature change (in degrees Fahrenheit) for Ohio from 1900 to 2100 as described in the caption.
Y-axis values range from negative 6 to positive 20 degrees. Observed annual temperatures from 1900 to 2024 show variability and range from negative 3.6 to positive 4.5 degrees. By the end of the century, projected increases in temperature range from 2.4 to 8.5 degrees under the lower emissions pathway, from 4.6 to 10.7 degrees under the intermediate pathway, and from 8.7 to 17.4 degrees under the higher pathway.
Annual average temperatures in Ohio have increased almost 2°F since the beginning of the 20th century, and temperatures in the 2000s and 2010s were warmer than in any other historical period (Figure 1). The warming has not been steady. The 1930s through the mid-1950s saw temperatures generally above the long-term average, but this was followed by the coldest period on record: the 1960s and 1970s. Since the 1970s, annual average temperature has increased more than 3°F. Ohio’s hottest year on record was 2024, with an annual average temperature of 54.9°F, more than 4°F above the long-term average (1895–2024) of 50.7°F. This warming has been concentrated in the winter and spring. Summer days have not warmed substantially in the state, a feature characteristic of much of the Midwest. This lack of summer warming is reflected in a generally below-average occurrence of very hot days since the late 1950s (Figure 2a). However, summer average nighttime temperatures have risen in recent years, with an upward trend in the number of warm nights since the 1960s (Figure 2b). Although Ohio has generally experienced a near- to below-average number of very cold nights since the 1990s, the number of such nights was very high during the winters of 2013–14 and 2014–15 (Figure 3), when temperatures from both December–February periods dropped more than 3.5°F below average as a result of a persistent pattern of frigid Arctic air (known as the polar vortex) that descended over the eastern US. Although the state averages approximately 6 very cold nights annually, the 2013–14 and 2014–15 winters saw 18 and 20 very cold nights, respectively.
Two graphs of the observed annual number of (a) very hot days and (b) warm nights for Ohio from 1900 to 2024 as described in the caption.
Panel A: Very Hot Days
Y-axis values range from 0 to 24 days. Annual values show year-to-year variability and range from 0 to 20.6 days. Five-year values also show variability and are mostly near or above the long-term average of 3.5 days between 1900 and 1954 but are all below average since 1955. The 2015 to 2019 period has the lowest 5-year value at 0.4 days, and the 1930 to 1934 period has the highest at 14.2 days.
Panel B: Warm Nights
Y-axis values range from 0 to 14 nights. Annual values show year-to-year variability and range from 0.7 to 11.5 nights. Five-year values also show variability and are all below the long-term average of 4.1 nights between 1905 and 1929; the 1900 to 1904 period is above average. Five-year values are all above average between 1930 and 1944 but are all below average between 1945 and 2004 except for the 1989 to 1989 and 1995 to 1999 periods. Since 2000, all 5-year values are above average. The 1960 to 1964 period has the lowest 5-year value at 1.3 nights, and the 1930 to 1934 period has the highest at 7.6 nights.
Graph of the observed annual number of very cold nights for Ohio from 1900 to 2024 as described in the caption.
Y-axis values range from 0 to 24 nights. Annual values show year-to-year variability and range from 0 to 22.6 nights. Five-year values also show variability and are all near or above the long-term average of 5.9 nights between 1900 and 1919, all below average between 1920 and 1959, and all near or above average between 1960 and 1989. Since 1990, 5-year values are all below average except for the 2015 to 2019 period. The 2020 to 2024 period has the lowest 5-year value at 2.3 nights, and the 1975 to 1979 period has the highest at 12.5 nights.
Statewide total annual precipitation has ranged from a low of 26.8 inches in 1963 to a high of 56.0 inches in 2011 (Figure 4). Seasonal precipitation is variable, with no overall trend in winter or summer precipitation; however, precipitation totals for both seasons have generally been near or above the long-term average since the 1990s (Figures 5a and 5b).
Graph of the observed total annual precipitation for Ohio from 1895 to 2024 as described in the caption.
Y-axis values range from 24 to 60 inches. Annual values show year-to-year variability and range from 26.8 to 56.0 inches. Five-year values also show variability and are below the long-term average of 38.9 inches between 1895 and 1904, all near or above average between 1905 and 1929, and mostly below average between 1930 and 1969. Since 1970, 5-year values are all near or above average except for the 1985 to 1989 period. The 1930 to 1934 and 1960 to 1964 periods have the lowest 5-year values at 33.56 and 33.64 inches, respectively, and the 2015 to 2019 period has the highest at 44.7 inches.
Two graphs of the observed total (a) winter and (b) summer precipitation for Ohio from 1895–96 to 2023–24 and 1895 to 2024, respectively, as described in the caption.
Panel A: Total Winter Precipitation
Y-axis values range from 2 to 18 inches. Annual values show year-to-year variability and range from 3.5 to 15.8 inches. Five-year values also show variability and are all near or above the long-term average of 8.0 inches between 1895 and 1939 except for the 1930 to 1934 period, but they are mostly near or below average between 1940 and 2004. Since 2005, all 5-year values are above average. The 1940 to 1944 period has the lowest 5-year value at 5.9 inches, and the 1950 to 1954 period has the highest at 10.2 inches.
Panel B: Total Summer Precipitation
Y-axis values range from 4 to 20 inches. Annual values show year-to-year variability and range from 6.4 to 18.7 inches. Five-year values also show variability and are mostly near or below the long-term average of 11.6 inches between 1895 and 1969 but are all near or above average since 1970 except for the 1985 to 1989 period. The 1930 to 1934 period has the lowest 5-year value at 9.7 inches, and the 2015 to 2019 period has the highest at 13.6 inches.
Ohio has seen an upward trend in the number of 2-inch extreme precipitation events since the middle of the 20th century; however, the 2020–2024 period was slightly below average (Figure 6). Past episodes of heavy rainfall have caused severe flooding in the state. The Great Flood of 1913 was one of the deadliest floods in US history and Ohio’s greatest weather disaster. From March 23 to 26, heavy rains caused extreme runoff from soils saturated by winter storms. Levees along the Great Miami River failed, flooding the entire watershed. Downtown Dayton was hit particularly hard, with floodwaters reaching depths of 20 feet. The flooding caused more than $2 billion in damages and more than 400 fatalities. One of the worst floods in recent decades occurred during March 1–3, 1997, when 6–12 inches of rain fell in parts of southern Ohio, causing serious flooding, particularly along Brush Creek and the Scioto and Great Miami Rivers. Water levels on the main stem of the Ohio River were the highest in more than 30 years. Seventeen counties were declared federal disaster areas, and more than 5,000 homes were damaged or destroyed, resulting in almost $300 million in damages.
Graph of the observed annual number of 2-inch extreme precipitation events for Ohio from 1900 to 2024 as described in the caption.
Y-axis values range from 0.0 to 3.0 events. Annual values show year-to-year variability and range from 0.1 to 2.5 events. Five-year values also show variability and are mostly near or below the long-term average of about 1.0 events between 1900 and 1989. One exception is the 1910 to 1914 period, which has the highest 5-year value at 1.4 events. Between 1995 and 2019, 5-year values are all above average, while the 2020 to 2024 period is below average. The 1930 to 1934 period has the lowest 5-year value at 0.6 events.
Dangerous storms can occur in every season and cause major impacts, including loss of life, property damage, and disruptions to economic activity. Winter can bring snowstorms and ice storms, while convective storms (including thunderstorms, flood-producing rainstorms, hailstorms, and tornadoes) are common in the warmer months. Although Ohio does not experience as many tornadoes as other states in the Midwest and Great Plains, the state has experienced several deadly tornado outbreaks. On June 28, 1924, Ohio’s deadliest tornado struck the towns of Sandusky and Lorain, killing 85 people and causing more than a billion dollars in damages. Other notable storms include the Palm Sunday Outbreak on April 11, 1965, which produced 10 tornadoes in the state (4 of which were F4 intensity) and caused 60 deaths; the Xenia tornado (F5 intensity) in the Super Outbreak of 1974, which killed 34 people; and the outbreak of April 8–9, 1999, which produced 54 tornadoes, including an F4-intensity tornado in Blue Ash and Montgomery that killed 4 people.
Agriculture, an important sector of Ohio’s economy, is particularly vulnerable to extreme weather conditions. In 2007, unusually warm March temperatures were followed by a hard freeze in April, which devastated much of the state’s apple crop. This scenario was again observed both in 2012 and 2021, when above-average March temperatures were followed by hard freezes in April. In 2012, an intense drought throughout the Midwest had severe impacts on Ohio. Rainfall totals for the summer were several inches below average. In addition to low precipitation amounts, the period from January to June was the warmest in 130 years of recordkeeping (1895–2024), with the warm temperatures compounding the dry conditions. By the end of the year, 86 of Ohio’s 88 counties had been declared drought disaster areas. Ohio also experienced widespread, intense drought in summer and fall 2024. By late September, 88% of the state was experiencing drought, with more than 35% of Ohio under extreme or exceptional drought conditions (as defined by the US Drought Monitor); however, modern drought monitoring tools and response strategies helped mitigate the impact on farmers and communities.
Between the months of July and October, northern Ohio is often affected by harmful algal blooms (HABs) on Lake Erie. HABs are caused by cyanobacteria (blue-green algae) fueled by high lake temperatures, slow-moving water, nutrient-rich runoff, and other factors; peak blooms often occur in August and September. Heavy rainstorms can exacerbate HAB conditions due to increased amounts of phosphorus being flushed into the lake. Toxins produced by these blooms pose a risk to both wildlife and people, forcing cities to close beaches and increase treatment of water supplies. In the Lake Erie region, the annual economic impact from HABs is estimated at more than $70 million, largely from a reduction in recreational activities such as swimming, boating, and fishing. Warming lake waters can increase the growth of HABs, which have become more prevalent in recent years.
Under the intermediate and higher emissions pathways, historically unprecedented warming is projected during this century (Figure 1). Even under the lower emissions pathway, most projections show annual average temperatures exceeding historical levels by the middle of the century. However, projections for all three pathways show a large range of potential temperature increases, and some projections for the lower pathway are comparable to recent observed values. Increases in extreme heat are a particular concern for Cincinnati, Columbus, and other urban areas, where high temperatures combined with high humidity can create dangerous heat index values and pose serious health risks. Heat absorbed and emitted by buildings and pavement, as well as other aspects of urban environments, makes cities even warmer than the surrounding countryside, a phenomenon known as the urban heat island effect. From July 17 to 24, 2011, the Ohio River Valley experienced a prolonged heat wave. With temperatures above 90°F for several days in a row and dewpoints in the mid- to upper 70s, heat index (a measure that combines air temperature and relative humidity) values rose to between 100° and 110°F during the day. These occurrences are expected to become more common as temperatures continue to rise, while cold waves are projected to decrease.
Under the intermediate emissions pathway, statistically significant increases in total spring precipitation are projected by midcentury across the northern half of Ohio and along its western border but are less certain elsewhere (Figure 7). Statistically significant increases are also projected for annual precipitation (across much of the northern half of the state) and winter precipitation (along the northern and eastern borders). There is uncertainty in projections for summer and fall precipitation. In addition, the frequency and intensity of extreme precipitation events are projected to increase, potentially resulting in increased flooding. Springtime flooding, in particular, could threaten Ohio’s agricultural industry by delaying planting and reducing crop yields.
Map of the contiguous United States showing the projected changes in total spring precipitation by the middle of this century as described in the caption. The state of Ohio is outlined in black.
Legend values range from less than negative 10 to greater than positive 15 percent. Note: unless otherwise specified, projected values are not statistically significant.
Ohio
Projected increases in total spring precipitation for Ohio are as follows: 5 to 10 percent across the majority of the state, with statistically significant increases in that range across the north-central and northeastern region and along the southwestern border, as well as statistically significant increases of 10 to 15 percent in the northwestern corner.
Contiguous US
Projected increases in total spring precipitation are as follows: up to 5 percent across a narrow strip running westward and curving northwestward from western Georgia into the Pacific Northwest; 5 to 10 percent in the Southeast, Mid-Atlantic, and Northeast, as well as southern areas of the Midwest, central portions of the Great Plains, and portions of the Northwest; and 10 to 15 percent in the northern areas of the Northeast, Midwest, and Great Plains, with statistically significant increases in the 10 to 15 percent range across the northern border of the country stretching from Maine to Montana. Decreases of up to 10 percent are seen across the southern Great Plains and Southwest, including southern Texas, all of Arizona, and most of New Mexico and California.
Droughts, a natural part of Ohio’s climate, are projected to increase in intensity due to higher temperatures and the associated increase in evaporation rates and soil moisture loss.
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