Coolest US Cities in Summer

Among major cities in the United States, it is San Francisco which tops the list for having the coldest weather overall in June, July and August. San Francisco's mean summer temperature is barely above 60 degrees Fahrenheit, whereas most large US cities average at least 70 degrees Fahrenheit (21 °Celsius) during summer.

The ratings below of coldest cities use long-term temperature averages for the three summer months, June, July and August, based on weather data collected from 1991 to 2020 for the US National Centers for Environmental Information. The major cities included in these weather rankings represent the 51 metropolitan areas in the United States with the most people, all those with over one million residents in 2010, according to the US Census Bureau.

Lowest Overall Temperature

Nine major US cities have a daily mean temperature for summer that is less than 72 °F.

US cities with the lowest normal daily mean temperatures for June, July and August
City Mean °F Mean °C
San Francisco, California 61 16
Seattle, Washington 66 19
Portland, Oregon 67 20
San Jose, California 69 21
Buffalo, New York 70 21
San Diego, California 70 21
Rochester, New York 70 21
Milwaukee, Wisconsin 71 22
Pittsburgh, Pennsylvania 71 22

City links take you to more detailed information on temperatures for that location. You can also view a summary of temperature averages for all major US cities and city temperatures in recent years and a complete list of America's 51 largest urban centers.

Coolest Summer Days

San Francisco keeps a cool average by seldom heating up over 79 °F. It typically sees just five days a year with temperatures in the 80s or 90s, and none in the 100s.

Other cities that normally don't reach 100 °F are Buffalo, Cleveland, Miami, Pittsburgh, Rochester, San Diego and Tampa. But not all of those cities have cool summer weather. Miami and Tampa spend over two-thirds of their summer days with highs in the 90s.

These large cities average fewer than ten days a summer with temperatures in the 90s

Number of days in summer with temperatures at or above 80 or 90 °F
City 80 °F
27 °C
90 °F
32 °C
San Diego, California 12 0
San Francisco, California 5 1
Buffalo, New York 43 3
Seattle, Washington 24 4
Rochester, New York 49 7
Milwaukee, Wisconsin 45 8
Pittsburgh, Pennsylvania 61 9
San Jose, California 46 9

Lowest Temperatures at Night

Nighttime temperatures in summer don't normally go below 40 °F (4 °C) at any of America's largest cities. Yet only five cities can count on every summer night cooling down to less than 71 °F (22°C): Denver, Portland, San Jose, Seattle and of course, San Francisco.

Here are the major cities that most often have summer nights when the thermometer dips into the 40s.

Number of days in summer when the temperature drops to 50 or 60 °F or below
City 50 °F
10 °C
60 °F
16 °C
Portland, Oregon 11 79
Denver, Colorado 11 68
Seattle, Washington 10 85
Rochester, New York 9 50
Salt Lake City, Utah 6 31
Hartford, Connecticut 6 42
Milwaukee, Wisconsin 5 37
Buffalo, New York 5 43
Reference

NOAA National Centers for Environmental Information (NCEI). Climate Normals.

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