Monthly Climate
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Best time to visit Portland

September is the best time to visit Portland for general sightseeing, with average highs of 25 °C and about 6 wet days. The comfortable season runs roughly June to September.

It depends what you are going for

One month rarely wins on everything. These are the best months on each measure taken on its own.

If you want Best month On that measure
Sightseeing and walking September comfort 92/100
The least cloud August 35 % average cloud cover
The least rain July 13 mm
Warmth August 29 °C
Cooler weather December 7.9 °C

Ranked by comfort

# Month Comfort / 100 Avg high Wet days
1 September 92 25 °C 6
2 June 91 23 °C 8
3 July 87 28 °C 3
4 August 85 29 °C 3
5 May 81 20 °C 12
6 October 73 18 °C 12
7 April 58 16 °C 17
8 March 45 13 °C 18
9 November 41 11 °C 17
10 February 40 11 °C 15
11 January 29 8.5 °C 17
12 December 26 7.9 °C 18

When to think twice

December scores lowest with about 18 wet days and highs near 7.9 °C. That does not make it a bad month — it depends entirely on what you are travelling for. The numbers are all here; the judgement is yours.

The full year

Month Avg high Rainfall Cloud
January 8.5 °C 168 mm 77 %
February 10.5 °C 130 mm 72 %
March 13.1 °C 146 mm 74 %
April 15.8 °C 116 mm 70 %
May 19.9 °C 72 mm 65 %
June 23.0 °C 46 mm 58 %
July 28.2 °C 13 mm 36 %
August 28.8 °C 15 mm 35 %
September 25.2 °C 44 mm 42 %
October 17.7 °C 107 mm 60 %
November 11.3 °C 175 mm 74 %
December 7.9 °C 194 mm 78 %

Data sources and method

Normal period
1991–2020
Dataset version
era5-1991-2020-scores1.1
Last processed

Measured values come from ERA5 reanalysis and are reproduced unchanged. Calculated by us: comfort score, beach score, season boundaries. Full formulas are on the methodology page.

Contains modified Copernicus Climate Change Service information 2026. Neither the European Commission nor ECMWF is responsible for any use that may be made of the Copernicus information or data it contains.