Happy Valley, Oregon Weather: December 2018

Happy Valley, Oregon Weather: December 2018

TEMPERATURES

It was a very mild month as temperatures were consistently above normal (22 total days averaged above normal at the Portland Airport, with all but 2 such days after December 10th). The middle of the month was the warmest. Splitting the month into thirds the following Max/Min/Mean Temperatures were observed: 1st-10th 43.6°/35.8°/39.7°; 11th-20th 52.6°/42.5°/47.6°; 21st-31st 45.6°/39.0°/42.3°. As is typical for this area in December, due to the more regular cloud cover, the diurnal range was quite low, averaging only 8.1° for the month; the maximum was 15.8° on the 14th, the minimum was 3.6° on the 28th.

Average Monthly Maximum: 47.2°
Average Monthly Minimum:  39.1°
Monthly Mean:  43.2°

 

Monthly High Maximum: 56.0° (20th)
Monthly Low Maximum:  40.2° (7th)
Monthly Low Minimum:   33.1° (7th)
Monthly High Minimum:  46.4° (19th)
Monthly High Mean: 50.4° (19th)
Monthly Low Mean: 36.7° (7th)

 

NUMBER OF DAYS:
Maximums ≥60°:    0
Maximums ≥55°:    3
Maximums ≥50°:  11
Maximums ≥45°:  22
Maximums ≥40°:  31
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Minimums ≤50°:  31
Minimums ≤45°:  29
Minimums ≤40°:  18
Minimums ≤35°:    7
Minimums ≤32°:    0

 

PRECIPITATION

It was a typically wet December as far as number of days of precipitation with measurable rain falling on 20 days. However, the total was quite a bit more than Normal with nearly 8 inches recorded, including 12 days with ≥0.25″. Only 0.14″ had fallen through the first 8 days (on just 2 separate days) so it appeared the much drier conditions through much of 2018 were going to continue, however 18 of the following 22 days would receive measurable rain. Pea-size Hail fell for a few minutes in the late evening on the 11th during the most intense short-term rain of the month (0.15″ in 4-minutes 2109-2013 Hrs (0.06″ in 1 minute ending 2112 Hrs)).

Total Precipitation: 7.93″
Maximum Calendar Day: 1.44″ (18th)

 

NUMBER OF DAYS OF PRECIPITATION & ATMOSPHERIC PHENOMENA:
≥0.01″: 20
≥0.25″: 12
≥0.50″:  5
≥1.00″:  2
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Thunder: 0
Hail: 1
Fog: 20
Heavy Fog: 2
Snowfall ≥Trace: 0
Snowfall ≥0.1″: 0
Snowfall ≥1.0″: 0
Snow Depth ≥Trace: 0
Snow Depth ≥1.0″: 0

 

MISCELLANEOUS

The month saw 6 Clear, 8 Partly Cloudy, and 17 Cloudy days; 20 days had Fog (2 of these being Heavy (≤ ¼ mile visibility)). The average wind speed was 0.6 MPH and the Maximum Gust reached 22 MPH (14th), noting that the anemometer is in a more protected location than standard. Relative Humidity remained high through most of the month, with only 7 days with a minimum falling below 70%, all in the first half of the month.

 

HAPPY VALLEY MONTHLY WEATHER FORM:   HAPPY-VALLEY-BELLA-CASA-WEATHER_2018-12.pdf

 

Cover Photo: Home Christmas lights, Dec. 2018. 

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