Last updated: January 18, 2025
The climate of Alderney, Guernsey, is classified under the Köppen-Geiger system as Cfb, indicative of a temperate oceanic climate. Characterized by mild temperatures throughout the year, it experiences a minimum of 0°C (32°F) in March, gradually rising to an average of 12°C (55°F). The warmest month sees maximum temperatures reaching 22°C (71°F) in August, contributing to the region's lush biodiversity and favorable conditions for outdoor activities. With its moderate climate, Alderney presents a unique environment well-suited for both residents and visitors alike.
Alderney, Guernsey experiences distinct seasonal temperature patterns throughout the year, characterized by mild winters and warm summers. January and February see cooler temperatures, with minimums around 0-3°C (32-37°F) and average highs peaking at 14°C (57°F) in January. As spring approaches in March and April, temperatures gradually rise, with averages reaching 10°C (50°F) by April, signaling the start of warmer days. By May, the climate becomes pleasantly warm, with maximums hitting 18°C (65°F). The summer months of July and August are the warmest, featuring average temperatures around 16-17°C (61-63°F) and peaks up to 22°C (71°F), which encourages outdoor activities. As autumn arrives, temperatures begin to decline again, with September retaining a mild feel before transitioning to cooler months in October and November, where averages hover around 12-15°C (54-59°F). This cyclical temperature pattern ensures Alderney is a temperate haven year-round, fostering its vibrant natural environment.
St Anne experiences a minimum temperature of 0°C (32°F) in March, while the maximum temperature peaks at 22°C (71°F) in August, showcasing a moderate climate throughout the year. For more details, you can refer to the monthly temperatures in St Anne.
Precipitation in Alderney, Guernsey exhibits a notable seasonal variation throughout the year, with the highest levels occurring during the winter months. January marks the wettest month, receiving 99 mm (3.9 in) of rainfall over approximately 15 days, while December follows closely with 170 mm (6.7 in), encompassing roughly 21 days of precipitation. February and March also experience significant rainfall, though slightly less intense, with totals of 86 mm (3.4 in) and 78 mm (3.1 in), respectively. This creates a damp winter environment that contributes to the island's lush greenery.
As spring progresses, precipitation levels begin to decline, reaching a low of 33 mm (1.3 in) in April, with just 7 days of rainfall. Summer months like July and August maintain a moderate level of precipitation, averaging around 38 mm (1.5 in) and 54 mm (2.1 in), respectively. However, autumn brings a resurgence in rainfall, with October and November recording 144 mm (5.7 in) and 131 mm (5.2 in) across 17 and 19 days of precipitation, respectively. This seasonal variability underscores the temperate maritime climate of Alderney, where weather patterns play a crucial role in shaping the island's natural landscape.
Alderney, Guernsey experiences a distinct seasonal pattern in sunshine duration, with hours of sunshine steadily increasing from the winter months into the vibrant summer. Starting from a modest 107 hours in January, the island sees a gradual uptick, culminating in a remarkable peak of 436 hours in July. March marks a significant turning point as sunlight begins to extend, with 238 hours, while April and May continue this upward trend, offering 359 hours and 414 hours respectively. June, often characterized by long daylight hours, rivals July, yielding 416 hours, further solidifying summer as the season of abundant sunshine.
As summer gives way to autumn, the sunshine hours begin to decline, reflecting the transition into a cooler climate. August still retains a generous 396 hours of sunlight, but September shows a noticeable drop to 338 hours. By the time October arrives, this downward trend continues with 270 hours, and the year closes with November and December presenting much shorter days, at 181 hours and 130 hours respectively. This seasonal variability in sunlight not only impacts the island's climate but also influences the lifestyle and activities of both residents and visitors, making summer a favored time for outdoor pursuits in Alderney.
The UV Index in Alderney, Guernsey reveals substantial variation throughout the year, reflecting seasonal changes in sun exposure. During the winter months, the UV Index remains low, with values of 2 in January and 2 in November, allowing for longer burn times of 45 minutes daily. In February and March, the index rises slightly to 3 and 4, respectively, denoting moderate exposure levels, while individuals can safely enjoy the sun for up to 30 minutes. This increase in UV levels indicates a gradual transition towards sunnier days, which culminates in the spring and summer months.
From April onwards, the UV Index escalates significantly, peaking at 9 in June, marking it as a period of very high risk for sunburn, with a shorter burn time of just 15 minutes. July follows closely with an 8 on the UV scale, while August also maintains a high 7 index. With the onset of autumn, UV levels begin to decline again, falling to 4 in October and back to lower levels of 2 and 1 in November and December, allowing for considerably longer intervals of safe sun exposure. This seasonal trend emphasizes the importance of sun safety measures during the summer months when the risk of UV-related skin damage is significantly heightened in Alderney.
UV Risk Categories
Daylight duration in Alderney, Guernsey exhibits a clear seasonal pattern, with significant variations from winter to summer. In January, residents experience only 8 hours of daylight, which gradually increases as the year progresses. By February, daylight lengthens to 10 hours, and reaches 11 hours in March. The increase in sunlight becomes more pronounced in April with 13 hours and continues to grow, peaking at an impressive 16 hours in June, providing ample time for outdoor activities and exploration during the vibrant summer months.
As summer transitions to autumn, daylight hours begin to shorten once again. In July, the duration remains robust at 15 hours, followed by a slight decline in August with 14 hours. By September, daylight decreases to 12 hours, and further diminishes to 10 hours in October. The trend continues, leading to November’s 9 hours and returning to 8 hours in December, the same as at the start of the year. This cyclical pattern of daylight availability underscores the importance of seasonal changes in Alderney, significantly impacting the daily life and activities of its inhabitants.
St Anne, Guernsey experiences a temperate maritime climate with mild winters and cool summers. Average temperatures range from a low of 1°C (33°F) in February to a high of 22°C (71°F) in August. Precipitation varies throughout the year, peaking in October with 144 mm (5.7 in), while April tends to be the driest month with only 33 mm (1.3 in). Sunshine hours are abundant during the summer months, reaching up to 436 hours in July, but taper off in winter. For more detailed information, visit St Anne climate.
In summary, the climate, sunlight, precipitation, and UV Index of Alderney, Guernsey create a unique environment that influences the lifestyle and natural beauty of the island throughout the year. With a temperate oceanic climate characterized by mild temperatures and distinct seasonal variations in sunshine and rainfall, Alderney offers vibrant summers with prolonged daylight and abundant sunshine, making it an appealing destination for outdoor enthusiasts. Conversely, the winter months bring shorter days and lower UV levels, emphasizing the need for seasonal awareness and sun safety. Overall, Alderney’s climate dynamics enrich its ecological diversity and enhance the quality of life for residents and visitors alike, inviting them to engage with its scenic landscapes year-round.