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 56 metropolitan areas in the United States with the most people, all those with over one million residents in 2020, according to the US Census Bureau.

Lowest Overall Temperature

Ten 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
Grand Rapids, Michigan	71	22
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 56 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, Grand Rapids, 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
Grand Rapids, Michigan	56	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
Grand Rapids, Michigan	8	47
Salt Lake City, Utah	6	31
Hartford, Connecticut	6	42
Milwaukee, Wisconsin	5	37
Buffalo, New York	5	43