The weather can vary considerably in an area as extensive as that covered by the National Park with its wide range of elevations.
Precipitation in low-lying areas south of the ice cap is considerable, ranging from 1,000 mm a year to 3,000 mm per year.
Temperatures in low-lying areas range between 10°C and 20°C in summer, while winters are rather mild (the thermometer rarely falls below -10°C and the temperature is often well above freezing point).
Mountains and ice cap
In the mountains and on the ice cap itself, annual precipitation can reach to between 4,000 and 5,000 mm, for the most part in the form of snow. The depth of snow on Öræfajökull after a high-precipitation winter is between 10 and 15 m. Some of the snow will melt, while the rest forms glacial ice. This process happens everywhere above the snowline on the Vatnajökull ice cap.
Temperatures on the southern part of the ice cap are almost always below zero in winter and can reach -20°C or -30°C. High winds and storms are common. Always remember to take wind-chill into account (see the website of the Icelandic Meteorological Office - www.vedur.is) as the wind can have a substantial effect on outdoor comfort, even when the ambient temperature is relatively high.
In the North
Further north beyond the ice cap, annual precipitation decreases. North-east of the ice cap it drops to between 350 and 450 mm per year, the lowest in Iceland. Precipitation increases closer to the north coast and in parts of the highlands such as at Askja. Temperatures can fall quite low in clear and calm weather during winter.
Southerly winds generally mean little or no precipitation in the north, along with higher temperatures. Northerly winds bring clouds, with cool and possibly wet weather in the north of the country, while the south is brighter and milder. The same applies to westerly or south westerly winds, which bring warmer weather in the east. The reverse is true of easterly winds, which bring coolness and precipitation in the east and dry, better weather in the west of Iceland. This is the result of the phenomenon of foehn winds. Humid, rather cool air rises as it nears the highlands; condensation then falls in the highlands as rain while warmer, drier air flows down to lower ground on the other side. The difference in temperature can be 10°C or greater.
Monitor weather forecasts while travelling - www.vedur.is and www.ruv.is provide online forecasts and details of radio broadcasts. Keep an eye on the weather at all times and equip yourselves in accordance with expected conditions in the area you will be visiting.
Cooling effects increase with altitude at a rate of 1°C for every 100 m increase in height. Winds may also be stronger at higher altitudes.
Where there is snow, it is important to get information on avalanches. Examine conditions carefully and avoid snow-covered slopes (see Avalanches on en.vedur.is).