Climate and Average Weather Year Round in Cook Islands Cook Islands
In Cook Islands, the summers are warm, oppressive, wet, and overcast; the winters are comfortable, muggy, and partly cloudy; and it is windy year round. Over the course of the year, the temperature typically varies from 69°F to 84°F and is rarely below 64°F or above 87°F.
Based on the tourism score, the best time of year to visit Cook Islands for warm-weather activities is from mid June to late September.
Climate in Cook Islands
The warm season lasts for 3.4 months, from January 2 to April 15, with an average daily high temperature above 83°F. The hottest month of the year in Cook Islands is February, with an average high of 84°F and low of 76°F.
The cool season lasts for 3.6 months, from June 14 to October 2, with an average daily high temperature below 78°F. The coldest month of the year in Cook Islands is August, with an average low of 69°F and high of 77°F.
Average High and Low Temperature in Cook Islands
The figure below shows you a compact characterization of the entire year of hourly average temperatures. The horizontal axis is the day of the year, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.
Average Hourly Temperature in Cook Islands
frigid 15°F freezing 32°F very cold 45°F cold 55°F cool 65°F comfortable 75°F warm 85°F hot 95°F sweltering
In Cook Islands, the average percentage of the sky covered by clouds experiences significant seasonal variation over the course of the year.
The clearer part of the year in Cook Islands begins around June 3 and lasts for 4.3 months, ending around October 14.
The clearest month of the year in Cook Islands is August, during which on average the sky is clear, mostly clear, or partly cloudy 59% of the time.
The cloudier part of the year begins around October 14 and lasts for 7.7 months, ending around June 3.
The cloudiest month of the year in Cook Islands is January, during which on average the sky is overcast or mostly cloudy 75% of the time.
Cloud Cover Categories in Cook Islands
0% clear 20% mostly clear 40% partly cloudy 60% mostly cloudy 80% overcast 100%
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days in Cook Islands varies significantly throughout the year.
The wetter season lasts 5.7 months, from November 28 to May 20, with a greater than 32% chance of a given day being a wet day. The month with the most wet days in Cook Islands is February, with an average of 12.8 days with at least 0.04 inches of precipitation.
The drier season lasts 6.3 months, from May 20 to November 28. The month with the fewest wet days in Cook Islands is June, with an average of 5.7 days with at least 0.04 inches of precipitation.
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 Cook Islands is February, with an average of 12.8 days. Based on this categorization, the most common form of precipitation throughout the year is rain alone, with a peak probability of 47% on February 13.
Daily Chance of Precipitation in Cook Islands
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. Cook Islands experiences extreme seasonal variation in monthly rainfall.
Rain falls throughout the year in Cook Islands. The month with the most rain in Cook Islands is January, with an average rainfall of 6.8 inches.
The month with the least rain in Cook Islands is August, with an average rainfall of 2.0 inches.
Average Monthly Rainfall in Cook Islands
The length of the day in Cook Islands varies over the course of the year. In 2021, the shortest day is June 20, with 10 hours, 50 minutes of daylight; the longest day is December 21, with 13 hours, 26 minutes of daylight.
Hours of Daylight and Twilight in Cook Islands
The earliest sunrise is at 5:48 AM on November 26, and the latest sunrise is 1 hour, 29 minutes later at 7:17 AM on July 4. The earliest sunset is at 6:04 PM on June 6, and the latest sunset is 1 hour, 23 minutes later at 7:26 PM on January 15.
Daylight saving time (DST) is not observed in Cook Islands during 2021.
Sunrise & Sunset with Twilight in Cook Islands
The figure below presents a compact representation of key lunar data for 2021. 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.
Moon Rise, Set & Phases in Cook Islands
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.
Cook Islands experiences extreme seasonal variation in the perceived humidity.
The muggier period of the year lasts for 8.4 months, from October 1 to June 14, during which time the comfort level is muggy, oppressive, or miserable at least 60% of the time. The month with the most muggy days in Cook Islands is March, with 30.6 days that are muggy or worse.
The month with the fewest muggy days in Cook Islands is August, with 14.7 days that are muggy or worse.
Humidity Comfort Levels in Cook Islands
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
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 Cook Islands experiences mild seasonal variation over the course of the year.
The windier part of the year lasts for 5.0 months, from June 2 to November 3, with average wind speeds of more than 13.6 miles per hour. The windiest month of the year in Cook Islands is September, with an average hourly wind speed of 14.2 miles per hour.
The calmer time of year lasts for 7.0 months, from November 3 to June 2. The calmest month of the year in Cook Islands is March, with an average hourly wind speed of 13.0 miles per hour.
Average Wind Speed in Cook Islands
The predominant average hourly wind direction in Cook Islands is from the east throughout the year.
Wind Direction in Cook Islands
Cook Islands 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 some seasonal variation over the course of the year.
The time of year with warmer water lasts for 3.4 months, from January 14 to April 25, with an average temperature above 80°F. The month of the year in Cook Islands with the warmest water is March, with an average temperature of 81°F.
The time of year with cooler water lasts for 3.7 months, from July 1 to October 24, with an average temperature below 77°F. The month of the year in Cook Islands with the coolest water is August, with an average temperature of 75°F.
Average Water Temperature in Cook Islands
To characterize how pleasant the weather is in Cook Islands 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 Cook Islands for general outdoor tourist activities is from mid June to late September, with a peak score in the first week of August.
Tourism Score in Cook Islands
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 Cook Islands for hot-weather activities is from early March to late December, with a peak score in the last week of March.
Beach/Pool Score in Cook Islands
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).
Temperatures in Cook Islands are sufficiently warm year round that it is not entirely meaningful to discuss the growing season in these terms. We nevertheless include the chart below as an illustration of the distribution of temperatures experienced throughout the year.
Time Spent in Various Temperature Bands and the Growing Season in Cook Islands
frigid 15°F freezing 32°F very cold 45°F cold 55°F cool 65°F comfortable 75°F warm 85°F hot 95°F sweltering
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.
Growing Degree Days in Cook Islands
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 some seasonal variation over the course of the year.
The brighter period of the year lasts for 4.1 months, from October 13 to February 17, with an average daily incident shortwave energy per square meter above 5.8 kWh. The brightest month of the year in Cook Islands is November, with an average of 6.3 kWh.
The darker period of the year lasts for 3.0 months, from April 29 to July 29, with an average daily incident shortwave energy per square meter below 4.1 kWh. The darkest month of the year in Cook Islands is June, with an average of 3.6 kWh.
Average Daily Incident Shortwave Solar Energy in Cook Islands
For the purposes of this report, the geographical coordinates of Cook Islands are -21.248 deg latitude, -159.785 deg longitude, and 0 ft elevation.
The topography within 2 miles of Cook Islands 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 Cook Islands is covered by water (100%), within 10 miles by water (100%), and within 50 miles by water (100%).
This report illustrates the typical weather in Cook Islands, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016.
The details of the data sources used for this report can be found on the Rarotonga International Airport page.
The information on this site is provided as is, without any assurances as to its accuracy or suitability for any purpose. Weather data is prone to errors, outages, and other defects. We assume no responsibility for any decisions made on the basis of the content presented on this site.
We draw particular cautious attention to our reliance on the MERRA-2 model-based reconstructions for a number of important data series. While having the tremendous advantages of temporal and spatial completeness, these reconstructions: (1) are based on computer models that may have model-based errors, (2) are coarsely sampled on a 50 km grid and are therefore unable to reconstruct the local variations of many microclimates, and (3) have particular difficulty with the weather in some coastal areas, especially small islands.
We further caution that our travel scores are only as good as the data that underpin them, that weather conditions at any given location and time are unpredictable and variable, and that the definition of the scores reflects a particular set of preferences that may not agree with those of any particular reader.