Portland, OR Weather Forecast and Current Conditions

Day		Sky	High / Low	Precip	Wind	Humidity
Wed May 14		Cloudy	-º / 48º	4%	SSW 5 mph	74%
Thu May 15		PM Light Rain View Hourly	58º / 49º	73%	WSW 5 mph	65%
3am		Cloudy	51º	2%	SW 4 mph	72%
4am		Cloudy	51º	3%	SSW 4 mph	73%
5am		Cloudy	51º	5%	SSW 4 mph	74%
6am		Cloudy	49º	5%	SSW 2 mph	77%
7am		Cloudy	49º	2%	SSW 2 mph	77%
8am		Cloudy	50º	2%	SW 2 mph	76%
9am		Cloudy	52º	2%	SW 2 mph	72%
10am		Cloudy	53º	5%	SW 3 mph	67%
11am		Cloudy	55º	6%	SW 4 mph	62%
12pm		Cloudy	56º	4%	WSW 4 mph	58%
1pm		Cloudy	57º	9%	WSW 4 mph	55%
2pm		Showers	57º	45%	W 4 mph	54%
3pm		Showers	57º	59%	WSW 4 mph	58%
4pm		Light Rain	57º	74%	W 4 mph	62%
5pm		Light Rain	56º	74%	WSW 4 mph	69%
6pm		Showers	55º	53%	W 4 mph	72%
7pm		Showers	55º	45%	W 4 mph	73%
8pm		Showers	55º	38%	W 4 mph	74%
9pm		Few Showers	53º	33%	WSW 3 mph	79%
10pm		Few Showers	52º	30%	WSW 3 mph	82%
11pm		Showers	52º	38%	SW 3 mph	82%
Fri May 16		Cloudy View Hourly	64º / 52º	24%	SSW 6 mph	70%
12am		Showers	52º	39%	SSW 3 mph	84%
1am		Few Showers	51º	30%	SSW 3 mph	86%
2am		Cloudy	51º	23%	SSW 3 mph	87%
3am		Cloudy	51º	21%	S 3 mph	88%
4am		Cloudy	51º	23%	S 3 mph	87%
5am		Cloudy	51º	20%	SSW 3 mph	88%
6am		Cloudy	50º	16%	S 3 mph	89%
7am		Cloudy	50º	14%	S 4 mph	89%
8am		Cloudy	51º	24%	S 4 mph	87%
9am		Few Showers	52º	32%	SSW 5 mph	84%
10am		Cloudy	54º	24%	SSW 5 mph	79%
11am		Cloudy	56º	13%	SSW 6 mph	74%
12pm		Cloudy	57º	12%	SSW 6 mph	70%
1pm		Cloudy	59º	8%	SSW 6 mph	66%
2pm		Cloudy	60º	4%	SSW 5 mph	62%
3pm		Cloudy	62º	2%	SW 4 mph	58%
4pm		Cloudy	63º	2%	SW 4 mph	56%
5pm		Cloudy	63º	7%	SW 3 mph	58%
6pm		Cloudy	62º	5%	WNW 4 mph	59%
7pm		Cloudy	62º	5%	N 3 mph	61%
8pm		Cloudy	61º	7%	N 3 mph	65%
9pm		Cloudy	59º	8%	NNW 2 mph	70%
10pm		Cloudy	58º	12%	NNW 3 mph	73%
11pm		Cloudy	57º	19%	NNW 2 mph	76%
Sat May 17		Showers View Hourly	62º / 47º	58%	W 9 mph	72%
12am		Showers	57º	38%	NW 2 mph	79%
1am		Showers	56º	55%	WNW 2 mph	82%
2am		Rain	55º	70%	W 2 mph	84%
Sun May 18		AM Showers	63º / 47º	33%	W 8 mph	60%
Mon May 19		AM Showers	65º / 49º	36%	SSW 9 mph	66%
Tue May 20		Mostly Cloudy	66º / 47º	23%	WSW 6 mph	60%
Wed May 21		Mostly Cloudy	68º / 48º	6%	NW 5 mph	53%

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General Weather Conditions in Portland, OR

The coast range provides limited shielding from the maritime influence of the Pacific Ocean. The Cascade Range provides a steep high slope for the lifting moisture-laden westerly winds, which produces heavy rainfall in the western Cascade piedmont region. They also form the barrier for the Columbia River basin region and dry continental air masses. Airflow is usually northwest in Portland in spring and summer and southeast in fall and winter, interrupted occasionally by outbreaks of dry continental air east through Cascade passes and across ridge tops. When such an outbreak occurs, extreme high or low temperatures are usually experienced in the Portland area.

Portland has a very definite winter rainfall climate. About 88 percent of the annual total occurs in October through May, nine percent in June and September, while only 3 percent comes in July and August. The average annual precipitation is 37.33 inches (948.2 mm). December is the wettest month, and July, the driest. Precipitation is mostly rain; on the average only 17 days each year have snow. Snowfall is seldom more than a couple of inches, and it generally lasts only a few days. The annual average is only seven inches (178 mm) with January having the most. Snowfall has fallen in every month from November through May. The greatest measured snowfall in 24 hours was just under 11 inches (279 mm) recorded in January 1971.

Each season is clearly marked. Winter is mild, cloudy and wet with southeast surface winds predominating. Summer is marked by mild temperature, with prevailing northwest winds and very little precipitation. Fall and spring are transitional in nature, with frequent periods of ground fog. An average of 18 days during October record foggy conditions while only three days during July can expect fog. At all times, incursions of marine-tempered air are a frequent moderating influence. Outbreaks of continental air from east of the Cascade Mountains flow through the Columbia Gorge at near sea level and spread into the Portland area associated with the movement of Pacific storms offshore on a northeast storm track. In winter this brings the coldest weather, and the extremes of low temperature are registered in the cold airmass. Freezing rain and ice glaze often are transitional effects. In summer the hot, dry, continental air brings the highest temperatures. Extreme temperatures below zero are very infrequent. The absolute lowest ever reached is 3°F below zero (-19.4°C) recorded in February 1950. Extreme temperatures above 100°F (37.8°C) have occurred during each month from May through September; the absolute highest temperature is 107°F (41.6°C) recorded in July 1942, July 1965 and August 1981. Temperatures 90°F (32.2°C) or higher are reached every year, but seldom persist for more than 2 or 3 days before the warm spell is broken by a flow of cool, moist air from the ocean. The average annual temperature for Portland is 53.9°F (12.1°C). The average maximum is 63°F (17.2°C) while the average minimum is 45°F (7.2°C).

Destructive storms are infrequent in the Portland area. Surface winds seldom exceed gale force. Thunderstorms are infrequent, occurring, on average, only seven days each year. Tornadoes with the funnel cloud reaching the ground are rare and there are rare occurrences of heavy rain even though winter rains may persist for days at a time. Ice forms occasionally, but it is seldom heavy enough to affect navigation seriously, although navigation by small craft may be difficult.