Monthly Climate
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Best time to visit Sunnyvale

October is the best time to visit Sunnyvale for general sightseeing, with average highs of 24 °C and about 3 wet days. The comfortable season runs roughly April to October.

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 October comfort 97/100
A beach holiday August sea 15 °C
The least cloud September 21 % average cloud cover
The least rain July 1 mm
Warmth August 28 °C
Cooler weather December 14 °C

Ranked by comfort

# Month Comfort / 100 Avg high Wet days Beach
1 October 97 24 °C 3 59
2 May 96 22 °C 3 52
3 June 94 26 °C 1 63
4 April 89 19 °C 6 38
5 September 89 27 °C 1 68
6 July 88 28 °C 0 65
7 August 87 28 °C 0 68
8 November 85 18 °C 6 33
9 March 77 17 °C 9 24
10 February 70 16 °C 10 18
11 January 65 15 °C 9 14
12 December 65 14 °C 9 13

For a beach holiday

August scores highest, with a sea temperature of 15 °C and air temperatures around 28 °C. The sea never reaches 20 °C here.

Month Sea Air Sunshine Beach score
January 12 °C 15 °C 58 % 14
February 12 °C 16 °C 58 % 18
March 12 °C 17 °C 57 % 24
April 12 °C 19 °C 49 % 38
May 12 °C 22 °C 42 % 52
June 13 °C 26 °C 28 % 63
July 14 °C 28 °C 22 % 65
August 15 °C 28 °C 22 % 68
September 15 °C 27 °C 21 % 68
October 14 °C 24 °C 31 % 59
November 13 °C 18 °C 47 % 33
December 13 °C 14 °C 55 % 13

When to think twice

December scores lowest with about 9 wet days and highs near 14 °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 14.6 °C 121 mm 58 %
February 15.8 °C 126 mm 58 %
March 17.4 °C 93 mm 57 %
April 19.4 °C 46 mm 49 %
May 22.1 °C 21 mm 42 %
June 25.5 °C 4 mm 28 %
July 27.5 °C 1 mm 22 %
August 27.7 °C 1 mm 22 %
September 27.4 °C 2 mm 21 %
October 23.8 °C 29 mm 31 %
November 18.0 °C 58 mm 47 %
December 14.2 °C 116 mm 55 %

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.