Warmer and Wetter Than Normal: IPMA's Seasonal Outlook Expects a Mild, Rainy Winter in Portugal From November to January

The months from November to January are more likely than not to be warmer and wetter than normal across Portugal, according to the latest seasonal forecast from the Portuguese weather institute IPMA, posted on 20 October. The bulletin (PDF, Portuguese only) expects mean temperatures on the mainland to run 1.0 to 1.5 °C above normal in each of the three months, with more rain than usual over most of the country, especially from December.

What the forecast says

• November: extra rain only north of the Montejunto and Estrela line, of 5 to 20 mm over the month, and over the western group of the Azores. No clear signal for the south or Madeira.
• December: the wetter signal spreads to the whole mainland and the rest of the Azores. The summary gives 5 to 15 mm above normal; the detailed page gives up to 20 mm for the mainland.
• January: 5 to 15 mm above normal on the mainland and in the Azores, 5 to 10 mm in Madeira.
• Temperature: 1.0 to 1.5 °C above normal on the mainland and 0.5 to 1.0 °C in Madeira in all three months; in the Azores, 0.5 to 1.0 °C, easing to 0.25 to 0.5 °C in December.

IPMA builds the outlook from the multi-model forecast of the EU's Copernicus Climate Change Service, which combines models from the European Centre for Medium-Range Weather Forecasts, the UK Met Office, Météo-France, Germany's DWD and others. It is a statement of probabilities, not a forecast of particular storms or cold snaps, and the extra rain is modest: a few millimetres to two centimetres on a monthly total.

Read it with care

IPMA is blunt about the limits. In its explanation of long-range forecasts it says the signals at seasonal scale are much weaker than in a normal forecast, errors build up over a far longer period, and users should treat the results with "the greatest care". It declines any responsibility for decisions taken on them.

IPMA's four-week outlook of 15 October points to a drier than normal week in the North and Centre to 25 October, then above-normal rain everywhere in the week from 2 November, with temperatures above normal for most of the period.

Where it lands

Rain would be welcome. IPMA's climate bulletin for September called the month extremely hot and very dry: the warmest September since 1931, at 2.91 °C above normal, with only 30 percent of normal rainfall. On 19 October the Portuguese Environment Agency's weekly reservoir bulletin put storage at 9,476 cubic hectometres, 72 percent of capacity, down 9 hm³ on the week. Lima, Cávado, Ave, Douro, Vouga and Mondego were all below their October average, a northern shortfall we reported earlier this month, and those are the basins where November's extra rain is forecast to fall.

What it means for your home

• Heating: a milder winter, if it comes, would mean fewer cold days, but it is an average. Cold spells still happen in a warm season, so plan heating on the bills you expect rather than the forecast.
• Rain and flooding: a wetter winter is a reason to clear gutters, drains and balcony outlets before December. Last winter's run of atmospheric rivers showed how fast heavy rain arrives.
• Warnings: follow IPMA's warnings page, issued by district for the next 72 hours. Yellow means stay alert; orange (moderate to high risk) and red (extreme risk) mean follow the civil protection authority ANEPC's advice, as IPMA's guide to its warnings sets out.

IPMA updates the seasonal outlook every month, so the picture for December and January may still change.