The Arctic Refuge is generally under the influence of two fairly extreme climates tenuously separated by the Brooks Range. North of the mountains the Arctic/maritime climate is strongly influenced by the Arctic Ocean which moderates seasonal temperature changes and often produces high winds and humidity. Weather changes here are frequent, quick and dramatic.

South of the Brooks, the geographically isolated Yukon Flats produces the most prominent continental climate in Alaska. The most extreme high and low temperatures in the state are recorded here along with relatively low average winds and humidity. Except for thunderstorm activity in the mid-summer, seasonal weather here is relatively stable.

The unpredictable mixing of such different weather systems gives rise to widely variable ranges of temperature, precipitation and wind at any given time throughout much of the Refuge, however, the following generally applies:

The onset of summer is evident by early June, but the progress of the spring thaw can vary considerably from year to year. It is conceivable to have significant remaining snow in the first half of June, especially in higher mountain passes, but also in the lower country of the coastal plain and foothills. Otherwise, conditions through June vary widely and you should expect a mix of cold, snow, rain, and wind as well as hot, dry conditions. Insects are not typically a significant consideration during most of June, however, there is some variation from year to year in their timing and intensity and they might be found anywhere in the refuge as early as the second week of June.

July has the most stable weather and the highest average temperatures. Snowfall in most areas other than along the coast is rare. Weather tends toward hot and dry, and otherwise comes as rain and wind associated with the movement of frontal systems and thunderstorms through the area. This is the month when mosquitoes and flies typically emerge, especially on the coastal plain and with varying intensity elsewhere.

Fall comes in August; days shorten noticeably and temperatures cool and fluctuate considerably between night and day. As in June, August weather is widely variable. Morning and evening fog, extending across the coastal plain and into the northern valleys of the mountains is common and delays in flying in these areas are more likely. Mosquitoes and flies tend to moderate substantially by early August and are usually a minor consideration after the second week of this month.

During the first half of September, the south side of the Brooks Range remains accessible for most activities. You can expect temperatures below freezing in the mornings, often rising into the 40’s (F.) during the day. The northern fog often extends into the southern foothills and Yukon Flats now and weather ranges from clear skies to overcast with rain. Usually you can rely on being in cool to cold conditions regardless of the cloud cover and precipitation. By mid-September, most of the leaves have fallen and access near the continental divide is often restricted by snowfall.

There are many sources for current and historical weather data, some of which are included in the Resources section of this site.