Climate and Average Weather Year Round in Rio Maior Portugal

In Rio Maior, the summers are warm, dry, and mostly clear and the winters are cold, wet, windy, and partly cloudy. Over the course of the year, the temperature typically varies from 43°F to 83°F and is rarely below 35°F or above 95°F.

Based on the beach/pool score, the best time of year to visit Rio Maior for hot-weather activities is from early July to late August.

The warm season lasts for 3.1 months, from June 17 to September 22, with an average daily high temperature above 78°F. The hottest month of the year in Rio Maior is August, with an average high of 82°F and low of 62°F.

The cool season lasts for 3.5 months, from November 18 to March 4, with an average daily high temperature below 62°F. The coldest month of the year in Rio Maior is January, with an average low of 43°F and high of 58°F.

In Rio Maior, 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 Rio Maior begins around June 5 and lasts for 3.3 months, ending around September 14.

The clearest month of the year in Rio Maior is July, during which on average the sky is clear, mostly clear, or partly cloudy 89% of the time.

The cloudier part of the year begins around September 14 and lasts for 8.7 months, ending around June 5.

The cloudiest month of the year in Rio Maior is December, during which on average the sky is overcast or mostly cloudy 51% of the time.

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days in Rio Maior varies throughout the year.

The wetter season lasts 7.9 months, from September 24 to May 21, with a greater than 17% chance of a given day being a wet day. The month with the most wet days in Rio Maior is November, with an average of 9.0 days with at least 0.04 inches of precipitation.

The drier season lasts 4.1 months, from May 21 to September 24. The month with the fewest wet days in Rio Maior is July, with an average of 0.8 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 Rio Maior is November, with an average of 9.0 days. Based on this categorization, the most common form of precipitation throughout the year is rain alone, with a peak probability of 31% on October 30.

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. Rio Maior experiences significant seasonal variation in monthly rainfall.

The rainy period of the year lasts for 9.5 months, from August 30 to June 15, with a sliding 31-day rainfall of at least 0.5 inches. The month with the most rain in Rio Maior is November, with an average rainfall of 3.2 inches.

The rainless period of the year lasts for 2.5 months, from June 15 to August 30. The month with the least rain in Rio Maior is July, with an average rainfall of 0.1 inches.

The length of the day in Rio Maior varies significantly over the course of the year. In 2024, the shortest day is December 21, with 9 hours, 24 minutes of daylight; the longest day is June 20, with 14 hours, 57 minutes of daylight.

The earliest sunrise is at 6:08 AM on June 13, and the latest sunrise is 1 hour, 49 minutes later at 7:57 AM on October 26. The earliest sunset is at 5:12 PM on December 7, and the latest sunset is 3 hours, 54 minutes later at 9:06 PM on June 27.

Daylight saving time (DST) is observed in Rio Maior during 2024, starting in the spring on March 31, lasting 6.9 months, and ending in the fall on October 27.

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.

The perceived humidity level in Rio Maior, as measured by the percentage of time in which the humidity comfort level is muggy, oppressive, or miserable, does not vary significantly over the course of the year, staying within 3% of 3% throughout.

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 Rio Maior experiences mild seasonal variation over the course of the year.

The windier part of the year lasts for 9.3 months, from November 9 to August 20, with average wind speeds of more than 9.0 miles per hour. The windiest month of the year in Rio Maior is July, with an average hourly wind speed of 9.8 miles per hour.

The calmer time of year lasts for 2.7 months, from August 20 to November 9. The calmest month of the year in Rio Maior is September, with an average hourly wind speed of 8.4 miles per hour.

The predominant average hourly wind direction in Rio Maior varies throughout the year.

The wind is most often from the north for 10 months, from January 15 to November 28, with a peak percentage of 73% on July 23. The wind is most often from the east for 1.6 months, from November 28 to January 15, with a peak percentage of 31% on January 1.

Rio Maior 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 3.8 months, from June 24 to October 18, with an average temperature above 64°F. The month of the year in Rio Maior with the warmest water is August, with an average temperature of 66°F.

The time of year with cooler water lasts for 3.7 months, from December 31 to April 21, with an average temperature below 59°F. The month of the year in Rio Maior with the coolest water is February, with an average temperature of 58°F.

To characterize how pleasant the weather is in Rio Maior 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 Rio Maior for general outdoor tourist activities is from early June to mid September, with a peak score in the second week of July.

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 Rio Maior for hot-weather activities is from early July to late 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).

While it does not do so every year, freezing temperatures are seen in Rio Maior over some winters. The day least likely to be in the growing season is January 6, with a 58% chance.

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 Rio Maior should appear around February 4, only rarely appearing before January 23 or after February 20.

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 3.2 months, from May 13 to August 20, with an average daily incident shortwave energy per square meter above 6.9 kWh. The brightest month of the year in Rio Maior is July, with an average of 8.0 kWh.

The darker period of the year lasts for 3.6 months, from October 25 to February 13, with an average daily incident shortwave energy per square meter below 3.2 kWh. The darkest month of the year in Rio Maior is December, with an average of 2.0 kWh.

For the purposes of this report, the geographical coordinates of Rio Maior are 39.337 deg latitude, -8.939 deg longitude, and 269 ft elevation.

The topography within 2 miles of Rio Maior contains significant variations in elevation, with a maximum elevation change of 564 feet and an average elevation above sea level of 338 feet. Within 10 miles contains significant variations in elevation (1,693 feet). Within 50 miles contains very significant variations in elevation (2,254 feet).

The area within 2 miles of Rio Maior is covered by trees (53%), cropland (29%), and artificial surfaces (17%), within 10 miles by cropland (51%) and trees (39%), and within 50 miles by water (32%) and trees (31%).