Environment Canada - Atlantic Climate Centre

• Introduction
• Oceanic Heat Pump
• Weather Mosaic
• Cloudy But Not Foggy
• Never Hot But Can Be Cold
• Wet And Breezy
• Wide Open To Storm Fury

Canada's Garden of the Gulf is surrounded by sea, lying between the Northumberland Strait on the south and west and the Gulf of St. Lawrence on the north and east. With the oceanic influence, the onset of the seasons is delayed several weeks. Winters are rambunctious but, on the whole, milder than in most parts of Canada. Spring is late and cool. Summer is modest and breezy. As for fall, well, Islanders will tell you they favour this season most of all, except when it involves the occasional brush with a dying Atlantic hurricane.

Oceanic Heat Pump

The island's gently rolling terrain, which generally does not rise any higher than 50 m above sea-level, presents no formidable obstacles to the weather systems that traverse the region. The sea is a much more important climate control, with no community farther than 20 km from the seashore. The seas about the Island function like a gigantic heat pump, drawing warmth from the waters in the fall and early winter and cooling the air for a greater part of the spring and summer seasons. From January to early April, when the gulf and straits become ice covered,the heat pump shuts down and the Island becomes as continental as the interior of New Brunswick.

Drift ice is often found around Island seas as late as the latter part of May, causing difficulty for fishermen and retarding the arrival of spring. The ice cover is by no means solid throughout this period, but is broken up by tides, strong winds, and occasional thaws. Just as weather profoundly affects the extent and duration of ice cover, so the relative amount of ice and water affects the weather, influencing the occurrence of fog cloud, snow, blowing snow, and extreme temperatures.

Weather Mosaic

Prince Edward Island has some of the most variable day-to-day weather experienced anywhere in the country. A specific set of weather conditions seldom lasts for long. The Island is affected by a mishmash of weather systems, bringing polar, maritime, continental, and tropical air from the Arctic Pacific, and Atlantic oceans and from the Gulf of Mexico. In summer the Island is visited most often by continental air from the west. Occasionally, warm tropical air is drawn in from the south. Winters are dominated by cold continental air masses, but storms originating in the North Pacific or the Gulf of Mexico frequently pass through, making winters stormy and unpredictable. The influence of moist Atlantic air often produces warm periods during the winter and cool weather during the summer.

Cloudy But Not Foggy

Cloud, mist, haze, and a bit of fog conspire to keep sunshine totals in P.E.I. below the national average, but not too far below. Its 1905 hours of bright sunshine are fairly close to the national average of 1925 hours. However, less than half the total possible sunshine occurs in every month and only 20% of the possible amount occurs in December.

The Island is relatively free of fog year- round, since neighbouring provinces help to shelter P.E.I. from fog-bearing southerly winds off the cool Bay of Fundy and the Atlantic Ocean. Even so, spring and summer are the foggiest seasons. At this time the ocean waters chill the warm, moist air masses moving over them, causing huge banks of persistent fog. Cold season fog results when the air is made moist and warm by contact with open water. Days with fog at Summerside number 37 a year, compared with 101 at Halifax (Shearwater) and 106 at Saint John.

Never Hot but Can Be Cold

Summers are pleasantly cool. The July average temperature is about 18.5C, with daily highs normally in the low to mid-twenties. Maximum temperatures exceed 30C only once or twice a year and have never exceeded 37.8C (100F) at any official weather station on P.E.I.

Winter temperatures reflect the presence of sea ice, becoming colder later in the winter after the surrounding sea-water freezes. Bitterly cold temperatures below -18C occur on only four or five nights in any winter, and thaws can occur in all the winter months. Periods free from frost extend over 130 days between late May and early October, a duration which compares favourably with that north of Lake Ontario and is about a month longer than the growing season on the southern Prairies.

Wet and Breezy

Precipitation is reliable and ample year- round. Annual totals average just under 1000 mm over the southeastern tip around Montague, increasing to 1100 mm or more in the centre of the Island at Charlottetown and New Glasgow. Monthly totals are greatest in the late fall and early winter, exceeding 100 mm monthly from October to January at Charlottetown, due to the more frequent and more intense storm activity at that time of the year. Wet days number 130 to 160 a year on the Island, with snow days accounting for 30% of them. Combined with the long growing season, the generous rainfall is responsible for the Island's verdant landscape and good farming.

Measurable snowfalls are frequent over the long winter season from November to April. The Island is one of the snowiest parts of Canada. Charlottetown's 330.6 cm makes it the third snowiest city next to St. John's and Quebec. However, because the snow comes and goes throughout the winter, there is an appreciable cover for only about three-quarters of the snow season, which lasts from late November to April 20, a period of about 145 days.

Heavy snowfalls of 12 cm or more average five a year, with one or two of them leaving as much as 25 cm of snow. The biggest snowfalls are usually associated with large, slow-moving weather systems and may last for up to 4 days.

Winds on the island are on average stronger than at most Maritime locations. The strongest winds occur in the coldest months, when stormy weather prevails. The lightest winds are summer breezes. Generally, winds from October to April are from the west or northwest; in summer, winds from the south and southwest predominate.

Wide Open to Storm Fury

The Island seldom experiences violent local storms in the form of tornadoes, severe thunderstorms, and hailstorms, although waterspouts, the aquatic cousins of tornadoes, are somewhat more in evidence. Thunderstorm days number between 9 and 12 a year on average considerably less than in other parts of southern Canada, and thunderstorms are certainly not of the same intensity as those experienced elsewhere. There are occasional exceptions, however. On July 17, 1980, heavy rains from a violent thunderstorm flooded parts of Charlottetown and blacked out the city for many hours.

Although local storms are rarely severe, the Island is vulnerable to the destructive forces of much more powerful Atlantic storms.These bring very high tides (storm surges), strong winds, and heavy rains. About once every summer and early fall, dissipating hurricanes tracking along the Atlantic coast expend their energy and remaining rainfalls over the Island. One of the most drenching and damaging storms of this kind occurred on September 22, 1942. Charlottetown recorded 163.8 mm of rain, the greatest daily total ever recorded for any P.E.I. station.

Winter storms pose a serious challenge. Packing a variety of weather conditions from hurricane force winds to heavy precipitation in all forms, they can pass rapidly through the region or stall and batter the province for days. Winds associated with these storms on occasion exceed 100 km/h. When such storms occur at high tide, storm surges become a problem. When the centres of the storms remain to the south of the Island, precipitation reaches the Gulf and the Island in the form of snow. If the low centre passes to the north of the Island, the snow will change to freezing rain and rain. Freezing rain and snowfall may combine to paralyse the Island for days, at great cost to communications and transportation. During an average year, about 40 hours of freezing rain or drizzle fall over Prince Edward Island, coating everything in sight.

Blizzards, which unleash the threat of snow, wind, and cold, strike the province with paralysing force about two or three times a winter.