If you were in mainland Portugal last month and felt like the heat never let up, the numbers back you up. The country's meteorological institute, IPMA, has confirmed that September 2024 was the hottest September since official records began in 1931, with an average maximum temperature of 31.03°C — a hefty 4.21°C above the norm.
The average overall temperature came in at 23.41°C, nearly three degrees higher than the 1991–2020 reference period. Even overnight lows were unusually warm, averaging 15.79°C and ranking as the fourth-highest minimum temperature on record. Two separate heatwaves hit the mainland during the month: a shorter one in the northern interior early in the month, and a much bigger one from the 18th to the 27th, which lasted up to 10 days and was registered at 72% of IPMA's weather stations, blanketing much of the country.
It wasn't just hot — it was bone dry. September was the fifth driest since 2000, with a cumulative rainfall of just 12.7mm, roughly 30% of what the month normally sees. Much of the mainland received below-normal rainfall throughout.
For travellers, this is a snapshot of how Portugal's shoulder season is shifting. September has long been a favourite month for visitors: the summer crowds thin out, the ocean is at its warmest, and prices ease off their August peaks. But these figures suggest that late-summer heat is no longer something you can count on escaping. If you're planning a September trip to Lisbon, Porto or the Algarve, it's worth booking accommodation with air conditioning, packing for beach weather rather than autumn, and scheduling sightseeing for mornings and evenings.
The drought side of the equation matters too. Water restrictions can affect rural areas, and wildfire risk stays elevated in hot, dry conditions — worth checking local alerts if your plans include hiking in the interior or the national parks.
None of this makes September a bad time to go. Portugal remains superb in early autumn, and many travellers will happily trade a few hot afternoons for quieter streets and warm sea. But the smart move is to plan for summer-like heat rather than assuming a gentle transition into autumn.
