This report describes the typical weather at the Hillsboro Airport (Portland, Oregon, United States) weather station over the course of an average March. It is based on the historical records from 1982 to 2012. Earlier records are either unavailable or unreliable.
Portland, Oregon has a mediterranean climate with dry warm summers and mild winters. The area within 25 mi of this station is covered by forests (62%), croplands (23%), built-up areas (11%), and lakes and rivers (4%).
The month of March is characterized by gradually rising daily high temperatures, with daily highs increasing from 53°F to 57°F over the course of the month, exceeding 67°F or dropping below 45°F only one day in ten.
Over the course of March, the length of the day is rapidly increasing. From the start to the end of the month, the length of the day increases by 1:36 hours, implying an average day-over-day increase of 3.1 minutes.
The shortest day of the month is March 1 with 11:11 hours of daylight; the longest day is March 31 with 12:46 hours of daylight.
The earliest sunrise is at 6:33am on March 10; the latest sunset is at 7:40pm on March 31; the latest sunrise is at 7:31am on March 11; the earliest sunset is at 6:00pm on March 1.
Daylight savings time (DST) starts at 3:00am on March 11, 2012, shifting sunrise and sunset to an hour later.
The median cloud cover is 93% (mostly cloudy) and does not vary substantially over the course of the month.
On March 16, a representative day, the sky is clear or mostly clear 25% of the time, partly cloudy 6% of the time, and mostly cloudy or overcast 68% of the time.
The average probability that some form of precipitation will be observed in a given day is 63%, with little variation over the course of the month.
Throughout March, the most common forms of precipitation are light rain and moderate rain.
Light rain is the most severe precipitation observed during 69% of those days with precipitation. It is most likely around March 29, when it is observed during 44% of all days.
Moderate rain is the most severe precipitation observed during 21% of those days with precipitation. It is most likely around March 14, when it is observed during 14% of all days.
The likelihood of snow falling is highest around March 1, occurring in 5% of days.
Either snow rarely accumulates at this location in March or snow depth measurements are unavailable or unreliable.
The relative humidity typically ranges from 53% (mildly humid) to 97% (very humid) over the course of a typical March, rarely dropping below 35% (comfortable) and reaching as high as 100% (very humid).
The air is driest around March 30, at which time the relative humidity drops below 63% (mildly humid) three days out of four; it is most humid around March 12, rising above 96% (very humid) three days out of four.
Dew point is often a better measure of how comfortable a person will find the weather than relative humidity because it more directly relates to whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid.
Over the course of a typical March, the dew point typically varies from 34°F (dry) to 44°F (dry) and is rarely below 24°F (dry) or above 51°F (very comfortable).
Over the course of March typical wind speeds vary from 0 mph to 13 mph (calm to moderate breeze), rarely exceeding 20 mph (fresh breeze).
The highest average wind speed of 6 mph (light breeze) occurs around March 19, at which time the average daily maximum wind speed is 13 mph (moderate breeze).
The lowest average wind speed of 5 mph (light breeze) occurs around March 1, at which time the average daily maximum wind speed is 12 mph (gentle breeze).