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Month guide · Mértola, Portugal

Mértola in September: weather and what to expect

September is the last month of the year with average highs above 25°C in Mértola. In September, Mértola is the warmest town in Portugal. In September, Mértola averages highs of 30°C and lows of 18°C, with about 4 rainy days and 24 mm of rain. Crowds in the Alentejo are medium.

Based on 1991-2020 climate data · Updated 1 November 2026 · Sources

Average high Town-level30°CLow 18°C
Rainy days Town-level424 mm in total
UV index Modelled7High at noon on a clear day
Crowds RegionalMediumThe Alentejo as a whole

Is September a good time to visit?

Good for

No verdicts for Mértola in September yet. They only use climate values that are precise enough to judge with.

Not ideal for

Nothing stands out as a weaker fit.

Daily highs through September

Town-level · ERA5-Land 1991-2020
Usual range (8 in 10 years)Typical high

Highs fall about 5°C over the month.

September in detail

Town-level · ERA5-Land
MeasureAugustSeptemberOctober
Average high34°C30°C24°C
Average low20°C18°C15°C
Rainy days (at least 1 mm)147
Total rainfall5 mm24 mm61 mm
Daylight (mid-month)13 h 40 min12 h 29 min11 h 17 min

Crowds, holidays and daylight

Visitor level RegionalMediumNights booked through online platforms in the Alentejo in September 2025: about 50% of the busiest month.

Public holidays in September 2027

No national or regional public holidays.

Local (municipal) holidays are not included.

Daylight mid-month Exact12 h 29 minSunrise to sunset, calculated from the town's coordinates.

Warmer in September

Where is warm in September →

No town in Portugal with precise enough data has a warmer average September high than Mértola.

How September is changing

Town-level · ERA5-Land

September highs are 2.1°C warmer than in 1991-2000, and September rainfall is about the same (2016-2025 against 1991-2000). Days above 35°C in September went from 1.6 to 3.5 a year on average.

Questions about Mértola in September

How warm is Mértola in September?

Average highs are 30°C and lows 18°C. August averages 34°C and October 24°C.

Does it rain much in Mértola in September?

About 4 days have at least 1 mm of rain, with 24 mm in total over the month.

Is Mértola busy in September?

In September 2025, nights booked through online platforms in the Alentejo were about 50% of the busiest month, which we count as medium. The figure is for the whole region and leaves out hotels.

How long are the days in Mértola in September?

About 12 h 29 min from sunrise to sunset in the middle of the month.

Sources

Climate: ERA5-Land, Copernicus Climate Change Service (C3S) Climate Data Store, contains modified Copernicus information (CC BY 4.0). Crowds: Eurostat, nights spent in short-stay accommodation booked through online platforms (tour_ce_omn12) (CC BY 4.0). Place names and populations: GeoNames (CC BY 4.0). Climate averages cover 1991-2020. Daylight: calculated from the town's coordinates. Full methodology