TEMPERATURES

September 2023 averaged around Normal in the Portland area; the three official Portland weather stations had Mean Temperature Departures ranging from -0.9° to +1.0°. See detailed data for Portland’s official stations at the end of the post.

Here in Happy Valley, the September Average Maximum/Minimum/Mean Temperatures were 71.3°/53.8°/62.6°. The month began relatively warm the first 2 days, with the Maximum Temperature reaching the mid-80s on the 2nd but quickly cooling to the 60s to mid-70s through the 8th. The warmest period of the month stretched from the 9th-16th when the Max. averaged 80.3°. However, this was to be the last of the above-normal Max. Temps. for the remainder of the month as it averaged 65.2° from the 17th-30th, mostly resulting from the measurable rain occurring from the 23rd-29th, providing an Avg. Max. of only 61.4° during this latter 7-day wet period. For the month, there were 5 days ≥80°, with 2 of these reaching ≥85°, while 9 days remained ≤65° and 3 of these being ≤60°.

Minimum Temperatures were not as variable as Max. Temps this month, with the first 17 days ranging from 50.1° on the 6th to 61.1° on the 15th (this September’s warmest Min. Temp.). Regularly cooler Min. Temps. began on the 18th, ranging from the mid-50s down to the mid-40s through month’s end (44.5° was the monthly Min. Temp. on the 21st). Overall, 20 days reached ≤55°, with 4 of these days being ≤50°.

The Average Monthly Diurnal Range was 17.4°; the Maximum being 30.0° on the 14th (84.2°/54.2°), the least was just 5.4° on the 29th (58.2°/52.8°).

 

HAPPY VALLEY SEPTEMBER 2023 STATISTICS:

 

HAPPY VALLEY MONTHLY WEATHER FORM: SEPTEMBER 2023 (click the month to access a pdf of the form).

 

 

For the three official Portland National Weather Service weather stations, here is Temperature and Precipitation data for each location for SEPTEMBER 2023:

Data Periods of Record for the three official Portland stations:

• Portland International Airport (PDX) – Period of Record: since 10/1940.
• Portland – Downtown (KGW-TV) – Period of Record: since 1/1871.
• Portland – National Weather Service Forecast Office (WFO) – Period of Record: since 2/1996.

 

For SEPTEMBER 2023, the 3 official Portland stations were near Normal temperature-wise, precipitation from a bit below to a bit above Normal:

 

 

SEPTEMBER 2023 Precipitation (and Departures, Percentages of Normal for the 30-Year Period 1991-2020):

• PDX Airport: 1.25″ (-0.27″, 82.2%)
• Downtown: 1.52” (-0.06”, 96.2%)
• WFO: 1.43″ (-0.22″, 86.7%)

 

THE SEPTEMBER 2023 MONTHLY TEMPERATURE & PRECIPITATION RECORDS SET:

Portland International Airport (PDX): 

• High Daily Mean: 76.0° (15th)
• Average Monthly Minimum Temperature: 56.7° ranked #5 warmest for September (tied with 2013 and 1940, this latter year being just prior to officially moving to PDX in October 1940)
• All-Time record Annual Number of Days with Maximum Temperatures of ≥80°: On 9/16/2023, PDX hit 85°, marking 91 days in 2023 reaching ≥80°, now ranking #1 all-time, surpassing the previous record  of 90 days from 2021.

 

Portland – Downtown (KGW-TV):

• High Daily Maximum: 85° (7th). 
• Annual Number of Days with Maximum Temperatures ≥80°: On 9/16/2023, the Downtown reached 83°, marking 72 days in 2023 reaching ≥80°, now ranking #4 all-time behind #2’s 73 days (tie) in 1958 & 2021, and #1’s 84 days in 1967.

 

Portland – National Weather Service Forecast Office (WFO): 

• High Daily Maximum Temperature: 93° (15th)
• Low Daily Maximum Temperatures: 65° (4th) and 59° (24th); Ranked #7 lowest September Max. Temp., tied with 9/28/2019, 9/18/2017, 9/14/2015, 9/6/2015, and 9/29/2007
• High Daily Mean Temperature: 74.5° (15th)
• Annual Number of Days with Maximum Temperatures ≥80°: On 9/16/2023, the WFO hit 85°, marking 86 days in 2023 reaching ≥80°, now ranking #3 all-time behind #2’s 87 days in 2015 and #1’s 88 days in 2021. 
• Annual Number of Days with Maximum Temperatures ≥90°: On 9/15/2023, the WFO hit 93°, marking 21 days in 2023 reaching ≥90°, now ranking #10 all-time, #1 being 32 days in 2018.