This report describes the typical weather at the Renton Municipal Airport (Renton, Washington, United States) weather station over the course of an average year. It is based on the historical records from 1988 to 2012. Earlier records are either unavailable or unreliable.
Renton, Washington has a mediterranean climate with dry warm summers and mild winters. The area within 25 mi of this station is covered by forests (64%), built-up areas (17%), oceans and seas (15%), and croplands (3%).
Over the course of a year, the temperature typically varies from 37°F to 78°F and is rarely below 28°F or above 87°F.
The warm season lasts from June 22 to September 15 with an average daily high temperature above 71°F. The hottest day of the year is July 26, with an average high of 78°F and low of 59°F.
The cold season lasts from November 14 to March 5 with an average daily high temperature below 52°F. The coldest day of the year is December 27, with an average low of 37°F and high of 46°F.
The length of the day varies significantly over the course of the year. The shortest day is December 21 with 8:26 hours of daylight; the longest day is June 20 with 15:59 hours of daylight.
The earliest sunrise is at 5:11am on June 18 and the latest sunset is at 9:11pm on June 22. The latest sunrise is at 7:57am on January 3 and the earliest sunset is at 4:17pm on December 11.
Daylight savings time (DST) is observed in this location during 2012, starting in the spring on March 11 and ending in the fall on November 4.
The median cloud cover ranges from 31% (mostly clear) to 98% (overcast). The sky is cloudiest on December 22 and clearest on August 14. The clearer part of the year begins around June 20. The cloudier part of the year begins around October 3.
On August 14, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 50% of the time, and overcast or mostly cloudy 32% of the time.
On December 22, the cloudiest day of the year, the sky is overcast, mostly cloudy, or partly cloudy 66% of the time, and clear or mostly clear 18% of the time.
The probability that precipitation will be observed at this location varies throughout the year. Precipitation is most likely around December 11, occurring in 66% of days. Precipitation is least likely around August 6, occurring in 21% of days.
Over the entire year, the most common forms of precipitation are light rain and moderate rain.
Light rain is the most severe precipitation observed during 71% of those days with precipitation. It is most likely around March 28, when it is observed during 46% of all days.
Moderate rain is the most severe precipitation observed during 17% of those days with precipitation. It is most likely around November 13, when it is observed during 14% of all days.
During the warm season, which lasts from June 22 to September 15, there is a 27% average chance that precipitation will be observed at some point during a given day. When precipitation does occur it is most often in the form of light rain (72% of days with precipitation have at worst light rain), moderate rain (12%), and thunderstorms (9%).
During the cold season, which lasts from November 14 to March 5, there is a 63% average chance that precipitation will be observed at some point during a given day. When precipitation does occur it is most often in the form of light rain (69% of days with precipitation have at worst light rain), moderate rain (19%), and light snow (5%).
The likelihood of snow falling is highest around January 17, occurring in 6% of days.
Either snow rarely accumulates at this location or snow depth measurements are unavailable or unreliable.
The relative humidity typically ranges from 44% (comfortable) to 95% (very humid) over the course of the year, rarely dropping below 32% (comfortable) and reaching as high as 100% (very humid).
The air is driest around August 4, at which time the relative humidity drops below 50% (mildly humid) three days out of four; it is most humid around October 29, exceeding 92% (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 year, the dew point typically varies from 32°F (dry) to 58°F (comfortable) and is rarely below 21°F (dry) or above 63°F (mildy humid).
The time of the year between May 20 and October 19 is the most comfortable, with dew points that are neither too dry nor too muggy.
Over the course of the year typical wind speeds vary from 0 mph to 14 mph (calm to moderate breeze), rarely exceeding 22 mph (fresh breeze).
The highest average wind speed of 8 mph (gentle breeze) occurs around July 12, at which time the average daily maximum wind speed is 13 mph (moderate breeze).
The lowest average wind speed of 6 mph (light breeze) occurs around October 15, at which time the average daily maximum wind speed is 11 mph (gentle breeze).