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SunnyDays

ERA5 almanac — 8 years of real data

Sydney in January

Sydney in January: 46% of days see measurable rain, 81°F average high, 31% of days historically clear (n=248, ERA5 2018–2025).

Sydney in January is historically a poor month for sun: only 31% of days clear across 8 years (n=248, avg high 81°F). Historical average, not a forecast.

What you are reading: 8-year historical averages from the ERA5 reanalysis, not a forecast. A month that is historically 90% clear can still be overcast on your specific trip. For this week’s actual forecast, see the live Sydney page. Both can be true at once: “historically strong in this month; this particular week is not.” We label which is which.

Early vs. Late January

Clear-sky percentage for Sydney in January, split by half-month. “n” is the number of days sampled across 8 years (2018–2025).
Period % Clear days Sample (n) Avg high
Early January
1st–15th		 27% n=120 81°F
Late January
16th–end		 34% n=128 81°F
Full month average 31% n=248 81°F

Sunshine & warmth in January

A second measure using actual sunshine hours (ERA5 sunshine_duration), not the daily weather code. A Lowcountry day with 12 hours of sun and a 25-minute afternoon storm is counted below as a warm, sunny day — because it was. How we define this.

Sunshine-based metrics for Sydney in January. Primary: % of days ≥ 72°F with > 6 h of sunshine.
Period Warm & sunny (≥72°F, >6 h sun) Sample (n)
Early January
1st–15th		 85% n=120
Late January
16th–end		 82% n=128
Full month average 83% n=248
12.0 h median sunshine per day 81% of days exceed 8 h sunshine 46% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 31%. Sunshine-based “warm & sunny”: 83%. The 52-point gap is from brief afternoon convective storms that stamp the whole day as “rain” in the WMO code but leave the bulk of the sunshine untouched.

Bottom line

Sydney is mostly overcast in January historically: only 31% of days are clear across 8 years (n=248), avg high 81°F. Most visitors this month will see more clouds than sun.

Every month in Sydney

Compare across all months with data. Numbers are historical clear-sky %.

Historical clear-sky % for Sydney, all months, ERA5 2018–2025.
Month % Clear Sample (n)
January ← this page 31% n=248 All destinations →
February 22% n=226 All destinations →
March 21% n=248 All destinations →
April 24% n=240 All destinations →
May 8% n=248 All destinations →
June 0% n=240 All destinations →
July 2% n=248 All destinations →
August 5% n=248 All destinations →
September 23% n=240 All destinations →
October 27% n=248 All destinations →
November 26% n=240 All destinations →
December 33% n=248 All destinations →

Frequently asked

Does it rain in Sydney in January?

Sometimes. Sydney sees measurable rain on 46% of days in January historically (n=248 days, ERA5 2018–2025) — not frequent enough to plan around, but not negligible either.

Is Sydney good for sun in January?

It's mixed. Sydney in January is clear on 31% of days historically (avg high 81°F, n=248 days, ERA5 2018–2025) — the outcome varies year to year.

All percentages are historical averages from the ERA5 reanalysis via Open-Meteo, 8 full years (2018–2025). “Clear” means avg high ≥ 72 °F, precipitation < 1 mm, and a non-precipitation weather code. This is history, not a forecast. The live 7-day outlook for any destination is on its own page and may differ from the long-run average. Data from Open-Meteo.