HAPPY VALLEY, OREGON WEATHER: DECEMBER 2020
TEMPERATURES
It was a very mild December as Average Temperatures were about 3° above the monthly Normal. Maximum Temperatures remained in the upper 40s to low 50s through the first 9 days, dropping to the low 40s from the 10th-13th, then rising again, even reaching 60.5° on the 21st for the warmest reading of the month. From the 22nd-31st, temperatures ranged from 49.4° to 39.2°, the latter reading being the lowest Maximum of the month on the 29th.
As far as Minimum Temperatures, only two days reached ≤32° and these waited until near month’s end (31.4° on the 24th and 30.7° on the 29th). The warmest period was 14th-20th when this 7-day average was just 43.6° as no Minimum fell below 40°, peaking at 48.5° on the 19th. Christmas Day was cloudy and had Maximum/Minimum/Average Temperatures of 47.6°/33.2°/40.4° with 0.31″ of rain falling at various periods of the day.
Splitting the month in half, the following Max/Min/Mean Temperatures were observed: 1st-15th 47.6°/37.9°/42.7°; 16th-31st 48.2°/39.5°/43.8°. The Maximum Diurnal Range was 20.6° (60.5°/39.9°) on the 21st, the least being just 3.2° (48.9°/45.7°) on the final day of 2020.
PRECIPITATION
Though it was a dry first 4 days, the month ended up being typically wet as 23 days had measurable rain. The total of 7.86″ was 102% of the normal of 7.22″. There was no major rain event through the first 17 days as only 2.82″ was recorded. A very wet system began affecting the area early evening on the 18th, ending late on the 22nd with the heaviest amounts falling during the 48-hour period late on the 19th to late on the 21st. A total of 4.27″ fell during these 5 days, with a calendar-day amount of 2.36″ on the 21st alone. The Maximum Rain Rate was 6.19″/Hr. at 1640 Hrs on the 21st. There were 9 days that recorded ≥0.25″ and 5 days ≥0.50″.
≥0.25″: 9
≥0.50″: 5
≥1.00″: 1
MISCELLANEOUS
Sky Cover: 5 Clear, 10 Partly Cloudy, and 16 Cloudy days.
Barometric Pressure ranged from a maximum of 30.57″ (1st) to a minimum of 29.61″ (21st).
Relative Humidity peaked at 100% (19th-21st) and reached a Minimum of 48% (2nd).
Dew Point went from a maximum of 62° (4th) to a minimum of 29° (9th).
Wind averaged 1.7 MPH and the Maximum Gust reached 28 MPH from the SE (21st).
MONTHLY WEATHER FORM: DECEMBER 2020
Cover Photo: Shadow from Mt. Jefferson at Sunrise, Dec. 3, 2020 at 0729 Hrs (shadow seen on right side of photo, Mt. Hood seen on left side).