As we operate in two different regions, there are two slightly different answers:
East Greenland, the Ammassalik region
The climate here is an arctic Polar climate. The weather is calm, dry, sunny, and cool in temperatures for most of the year.
In July, you can expect the temperature to be between 7°C to 13°C (45°F to 55°F) during the day and between 4°C to 8°C (39°F to 46°F) during the night. Most of the time it feels warmer than it actually is because calm and sunny weather is the norm. Even though in general weather is dry, it can rain and be windy so one has to prepare for the worst even though storms are very rare in summer.
In the big fjords, there is an afternoon breeze called fjord wind, strong enough to make afternoon boat rides a little bit bumpier than those in the morning, which often gives us the impression of sailing on a mirror.
In late August the dark nights come again and it is not uncommon for the temperature to drop down to freezing point during the night.
In September, night frost is common and during the day temperatures are typically between 4°C to 7°C (39°F to 45°F).
In winter, East Greenland’s climate is truly dominated by cold winter temperatures. Even though the weather is often calm, storms can be fierce in early winter. In March and April, the strength of the winter storms starts to ease out and even though storms with heavy snowfall and strong winds happen every now and then, the weather is generally much calmer and cooler than that of the closest neighbor, Iceland. Temperatures from -5°C to -20°C (23°F to -4°F) can be expected.
East Greenland has one unique weather type in winter, the Piteraq. This is when cold air is pushed over the Ice Cap from the West and with katabatic power (aka drainage winds or fall winds where high density air moves from high elevation to low)), takes up very high speed, pulled by gravity on the East side. These kinds of storms happen a few times a year and you will need to seek out good shelter when the Piteraqs (local term for “wind that attacks you”) are forecasted.
In the South, the fjords are quite deep and the climate is considerably milder at the bottom of the fjords compared to the opening. The climate here is in between temperate and arctic (polar) climates.
The summer comes earlier to South Greenland than in the East, and in June you can already expect some nice summer temperatures. In July, it is not uncommon to have temperatures ranging from 10°C to 15°C (50°F to 59°F) with the occasional days reaching up to almost 20°C (68°F). The region has slightly more precipitation during summer than the East, and even though most days are calm, fjord winds can be quite strong. In late August the temperatures start to drop but stay milder than in the East.
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