Climate and Average Weather Year Round in Saint John New Brunswick, Canada

In Saint John, the summers are comfortable; the winters are freezing, snowy, and windy; and it is partly cloudy year round. Over the course of the year, the temperature typically varies from 11°F to 72°F and is rarely below -5°F or above 79°F.

Based on the tourism score, the best time of year to visit Saint John for warm-weather activities is from early July to early September.

The warm season lasts for 3.5 months, from June 4 to September 20, with an average daily high temperature above 63°F. The hottest month of the year in Saint John is August, with an average high of 71°F and low of 56°F.

The cold season lasts for 3.2 months, from December 7 to March 14, with an average daily high temperature below 37°F. The coldest month of the year in Saint John is January, with an average low of 13°F and high of 29°F.

In Saint John, 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 Saint John begins around June 23 and lasts for 4.2 months, ending around October 29.

The clearest month of the year in Saint John is September, during which on average the sky is clear, mostly clear, or partly cloudy 60% of the time.

The cloudier part of the year begins around October 29 and lasts for 7.8 months, ending around June 23.

The cloudiest month of the year in Saint John is May, during which on average the sky is overcast or mostly cloudy 60% 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 Saint John varies throughout the year.

The wetter season lasts 9.9 months, from October 6 to August 3, with a greater than 29% chance of a given day being a wet day. The month with the most wet days in Saint John is December, with an average of 10.4 days with at least 0.04 inches of precipitation.

The drier season lasts 2.1 months, from August 3 to October 6. The month with the fewest wet days in Saint John is August, with an average of 8.0 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. Based on this categorization, the most common form of precipitation in Saint John changes throughout the year.

Rain alone is the most common for 11 months, from February 20 to January 12. The month with the most days of rain alone in Saint John is June, with an average of 9.3 days.

Snow alone is the most common for 1.3 months, from January 12 to February 20. The month with the most days of snow alone in Saint John is January, with an average of 3.6 days.

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. Saint John experiences significant seasonal variation in monthly rainfall.

Rain falls throughout the year in Saint John. The month with the most rain in Saint John is November, with an average rainfall of 4.0 inches.

The month with the least rain in Saint John is February, with an average rainfall of 1.7 inches.

Snowfall

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

The snowy period of the year lasts for 5.5 months, from November 5 to April 21, with a sliding 31-day snowfall of at least 1.0 inches. The month with the most snow in Saint John is January, with an average snowfall of 13.4 inches.

The snowless period of the year lasts for 6.5 months, from April 21 to November 5. The least snow falls around August 1, with an average total accumulation of 0.0 inches.

The length of the day in Saint John varies significantly over the course of the year. In 2024, the shortest day is December 21, with 8 hours, 44 minutes of daylight; the longest day is June 20, with 15 hours, 39 minutes of daylight.

The earliest sunrise is at 5:35 AM on June 15, and the latest sunrise is 2 hours, 30 minutes later at 8:05 AM on November 2. The earliest sunset is at 4:41 PM on December 9, and the latest sunset is 4 hours, 35 minutes later at 9:16 PM on June 25.

Daylight saving time (DST) is observed in Saint John 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.

The perceived humidity level in Saint John, 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 2% of 2% 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 Saint John experiences significant seasonal variation over the course of the year.

The windier part of the year lasts for 6.5 months, from October 4 to April 19, with average wind speeds of more than 8.2 miles per hour. The windiest month of the year in Saint John is January, with an average hourly wind speed of 10.3 miles per hour.

The calmer time of year lasts for 5.5 months, from April 19 to October 4. The calmest month of the year in Saint John is July, with an average hourly wind speed of 6.1 miles per hour.

The predominant average hourly wind direction in Saint John varies throughout the year.

The wind is most often from the south for 5.8 months, from April 11 to October 4, with a peak percentage of 51% on July 14. The wind is most often from the west for 6.2 months, from October 4 to April 11, with a peak percentage of 44% on January 1.

Saint John 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 3.4 months, from July 5 to October 17, with an average temperature above 52°F. The month of the year in Saint John with the warmest water is August, with an average temperature of 56°F.

The time of year with cooler water lasts for 4.0 months, from January 8 to May 9, with an average temperature below 39°F. The month of the year in Saint John with the coolest water is March, with an average temperature of 35°F.

To characterize how pleasant the weather is in Saint John 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 Saint John for general outdoor tourist activities is from early July to early September, with a peak score in the second 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 Saint John for hot-weather activities is from mid 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 Saint John typically lasts for 5.1 months (158 days), from around May 6 to around October 11, rarely starting before April 18 or after May 25, and rarely ending before September 26 or after October 26.

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 Saint John should appear around May 26, only rarely appearing before May 17 or after June 5.

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 3.4 months, from May 10 to August 23, with an average daily incident shortwave energy per square meter above 5.5 kWh. The brightest month of the year in Saint John is July, with an average of 6.4 kWh.

The darker period of the year lasts for 3.5 months, from October 29 to February 14, with an average daily incident shortwave energy per square meter below 2.3 kWh. The darkest month of the year in Saint John is December, with an average of 1.3 kWh.

For the purposes of this report, the geographical coordinates of Saint John are 45.273 deg latitude, -66.068 deg longitude, and 3 ft elevation.

The topography within 2 miles of Saint John contains only modest variations in elevation, with a maximum elevation change of 292 feet and an average elevation above sea level of 64 feet. Within 10 miles contains only modest variations in elevation (748 feet). Within 50 miles contains significant variations in elevation (1,450 feet).

The area within 2 miles of Saint John is covered by artificial surfaces (37%), water (26%), and trees (20%), within 10 miles by trees (53%) and water (36%), and within 50 miles by trees (50%) and water (45%).