|Information courtesy of the National Climate Data Center|
|Valdez is located on the Valdez Arm, a rather well sheltered extension of Prince William Sound. Snow-capped mountains, containing extensive glacier areas, extend almost continuously from southeast of Valdez through north to west-southwest, with rugged but normally unglaciated mountains to the south and southwest. Active glaciers extend to within 5 to 10 miles of Valdez to the north and reach down to the level of the glacial plain on which Valdez is located. This level glacial plain is for the most part a well forested area except for the tidal marshes east and the glacial drainage area further east.
The terrain surrounding Valdez exerts a pronounced influence on practically all aspects of the local weather and climate. The effects of the surrounding mountains are to channel the local winds. From October through April the prevailing direction is northeast, and from May through September the prevailing direction is from the southwest. During the winter, high pressure in the interior and low pressure in the gulf may cause east to north winds of about 100 knots to flow out of passes and river canyons.
Precipitation is abundant the year around, but builds up noticeably during late summer and fall. The heaviest precipitation usually occurs in September and October, and almost one-third of the total annual rainfall occurs in these two months. Snowfall during the winter months is very heavy. There is considerable cloudiness during the entire year, but slightly less than is realized at Alaskan points farther southeast.
Although the high mountain ridges to the north provide a considerable barrier to the flow of cold, continental air from the interior during the winter months, there is a definite offsetting factor in the downslope drainage from the snowfields and glacier areas on the southern slopes of these mountains. The coldest temperatures realized at Valdez appear to be related to the downslope flow of cold air, although temperatures only rarely dip below zero. The nearby snow and ice fields combine with the ocean areas to provide a moderating effect on the summertime high temperatures which have seldom reached the middle 80s. Considerable variations occur in practically all weather elements within relatively short distances.
The growing season averages slightly over 100 days, extending from May 26 to September 12. In addition, the glacier nature of the plain, the ruggedness of other surrounding terrain, and the cold water runoff from glacier melt tends to keep most available agricultural soil at temperatures too cool for desirable vegetation development during the growing season.