Climate and Average Weather Year Round in Cape Cod United States

In Cape Cod, the summers are warm; the winters are very cold, snowy, and windy; and it is partly cloudy year round. Over the course of the year, the temperature typically varies from 26°F to 78°F and is rarely below 14°F or above 85°F.

Based on the tourism score, the best time of year to visit Cape Cod for warm-weather activities is from late June to mid September.

The warm season lasts for 3.2 months, from June 9 to September 16, with an average daily high temperature above 70°F. The hottest month of the year in Cape Cod is July, with an average high of 77°F and low of 64°F.

The cold season lasts for 3.4 months, from December 9 to March 23, with an average daily high temperature below 45°F. The coldest month of the year in Cape Cod is January, with an average low of 27°F and high of 38°F.

In Cape Cod, the average percentage of the sky covered by clouds experiences mild seasonal variation over the course of the year.

The clearer part of the year in Cape Cod begins around June 25 and lasts for 4.4 months, ending around November 6.

The clearest month of the year in Cape Cod is September, during which on average the sky is clear, mostly clear, or partly cloudy 62% of the time.

The cloudier part of the year begins around November 6 and lasts for 7.6 months, ending around June 25.

The cloudiest month of the year in Cape Cod is May, during which on average the sky is overcast or mostly cloudy 54% of the time.

Cape Cod does not experience significant seasonal variation in the frequency of wet days (i.e., those with greater than 0.04 inches of liquid or liquid-equivalent precipitation). The frequency ranges from 24% to 33%, with an average value of 29%.

Among wet days, we distinguish between those that experience rain alone, snow alone, or a mixture of the two. The month with the most days of rain alone in Cape Cod is May, with an average of 9.4 days. Based on this categorization, the most common form of precipitation throughout the year is rain alone, with a peak probability of 32% on May 29.

Rainfall

To show variation within the months and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day of the year. Cape Cod experiences some seasonal variation in monthly rainfall.

Rain falls throughout the year in Cape Cod. The month with the most rain in Cape Cod is November, with an average rainfall of 4.1 inches.

The month with the least rain in Cape Cod is July, with an average rainfall of 2.7 inches.

Snowfall

As with rainfall, we consider the snowfall accumulated over a sliding 31-day period centered around each day of the year. Cape Cod experiences significant seasonal variation in monthly snowfall.

The snowy period of the year lasts for 4.2 months, from November 30 to April 4, with a sliding 31-day snowfall of at least 1.0 inches. The month with the most snow in Cape Cod is February, with an average snowfall of 5.0 inches.

The snowless period of the year lasts for 7.8 months, from April 4 to November 30. The least snow falls around July 22, with an average total accumulation of 0.0 inches.

The length of the day in Cape Cod varies significantly over the course of the year. In 2024, the shortest day is December 21, with 9 hours, 9 minutes of daylight; the longest day is June 20, with 15 hours, 12 minutes of daylight.

The earliest sunrise is at 5:05 AM on June 14, and the latest sunrise is 2 hours, 9 minutes later at 7:14 AM on November 2. The earliest sunset is at 4:10 PM on December 7, and the latest sunset is 4 hours, 9 minutes later at 8:19 PM on June 26.

Daylight saving time (DST) is observed in Cape Cod during 2024, starting in the spring on March 10, lasting 7.8 months, and ending in the fall on November 3.

The figure below presents a compact representation of key lunar data for 2024. The horizontal axis is the day, the vertical axis is the hour of the day, and the colored areas indicate when the moon is above the horizon. The vertical gray bars (new Moons) and blue bars (full Moons) indicate key Moon phases.

We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.

Cape Cod experiences significant seasonal variation in the perceived humidity.

The muggier period of the year lasts for 2.9 months, from June 19 to September 16, during which time the comfort level is muggy, oppressive, or miserable at least 10% of the time. The month with the most muggy days in Cape Cod is July, with 10.3 days that are muggy or worse.

The least muggy day of the year is February 23, when muggy conditions are essentially unheard of.

This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.

The average hourly wind speed in Cape Cod experiences significant seasonal variation over the course of the year.

The windier part of the year lasts for 6.0 months, from October 12 to April 14, with average wind speeds of more than 13.1 miles per hour. The windiest month of the year in Cape Cod is January, with an average hourly wind speed of 16.6 miles per hour.

The calmer time of year lasts for 6.0 months, from April 14 to October 12. The calmest month of the year in Cape Cod is July, with an average hourly wind speed of 9.7 miles per hour.

The predominant average hourly wind direction in Cape Cod varies throughout the year.

The wind is most often from the north for 1.1 months, from March 13 to April 15, with a peak percentage of 33% on March 17. The wind is most often from the south for 5.7 months, from April 15 to October 6, with a peak percentage of 43% on July 27. The wind is most often from the west for 5.2 months, from October 6 to March 13, with a peak percentage of 46% on January 1.

Cape Cod is located near a large body of water (e.g., ocean, sea, or large lake). This section reports on the wide-area average surface temperature of that water.

The average water temperature experiences significant seasonal variation over the course of the year.

The time of year with warmer water lasts for 2.9 months, from June 28 to September 25, with an average temperature above 61°F. The month of the year in Cape Cod with the warmest water is August, with an average temperature of 66°F.

The time of year with cooler water lasts for 4.0 months, from December 25 to April 25, with an average temperature below 44°F. The month of the year in Cape Cod with the coolest water is March, with an average temperature of 39°F.

To characterize how pleasant the weather is in Cape Cod throughout the year, we compute two travel scores.

The tourism score favors clear, rainless days with perceived temperatures between 65°F and 80°F. Based on this score, the best time of year to visit Cape Cod for general outdoor tourist activities is from late June to mid September, with a peak score in the last week of August.

The beach/pool score favors clear, rainless days with perceived temperatures between 75°F and 90°F. Based on this score, the best time of year to visit Cape Cod for hot-weather activities is from early July to mid August, with a peak score in the last week of July.

Methodology

For each hour between 8:00 AM and 9:00 PM of each day in the analysis period (1980 to 2016), independent scores are computed for perceived temperature, cloud cover, and total precipitation. Those scores are combined into a single hourly composite score, which is then aggregated into days, averaged over all the years in the analysis period, and smoothed.

Our cloud cover score is 10 for fully clear skies, falling linearly to 9 for mostly clear skies, and to 1 for fully overcast skies.

Our precipitation score, which is based on the three-hour precipitation centered on the hour in question, is 10 for no precipitation, falling linearly to 9 for trace precipitation, and to 0 for 0.04 inches of precipitation or more.

Our tourism temperature score is 0 for perceived temperatures below 50°F, rising linearly to 9 for 65°F, to 10 for 75°F, falling linearly to 9 for 80°F, and to 1 for 90°F or hotter.

Our beach/pool temperature score is 0 for perceived temperatures below 65°F, rising linearly to 9 for 75°F, to 10 for 82°F, falling linearly to 9 for 90°F, and to 1 for 100°F or hotter.

Definitions of the growing season vary throughout the world, but for the purposes of this report, we define it as the longest continuous period of non-freezing temperatures (≥ 32°F) in the year (the calendar year in the Northern Hemisphere, or from July 1 until June 30 in the Southern Hemisphere).

The growing season in Cape Cod typically lasts for 6.9 months (210 days), from around April 14 to around November 10, rarely starting before March 25 or after May 2, and rarely ending before October 21 or after November 29.

Growing degree days are a measure of yearly heat accumulation used to predict plant and animal development, and defined as the integral of warmth above a base temperature, discarding any excess above a maximum temperature. In this report, we use a base of 50°F and a cap of 86°F.

Based on growing degree days alone, the first spring blooms in Cape Cod should appear around May 12, only rarely appearing before May 2 or after May 21.

This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.

The average daily incident shortwave solar energy experiences extreme seasonal variation over the course of the year.

The brighter period of the year lasts for 3.3 months, from May 7 to August 18, with an average daily incident shortwave energy per square meter above 5.9 kWh. The brightest month of the year in Cape Cod is June, with an average of 6.8 kWh.

The darker period of the year lasts for 3.4 months, from November 2 to February 13, with an average daily incident shortwave energy per square meter below 2.7 kWh. The darkest month of the year in Cape Cod is December, with an average of 1.7 kWh.

For the purposes of this report, the geographical coordinates of Cape Cod are 41.686 deg latitude, -70.243 deg longitude, and 0 ft elevation.

The topography within 2 miles of Cape Cod is essentially flat, with a maximum elevation change of 0 feet and an average elevation above sea level of 0 feet. Within 10 miles is also essentially flat (0 feet). Within 50 miles is also essentially flat (0 feet).

The area within 2 miles of Cape Cod is covered by artificial surfaces (53%) and trees (41%), within 10 miles by water (61%) and artificial surfaces (21%), and within 50 miles by water (80%) and trees (12%).