Week of 21 to 27 September 2026: summer lingers and rain has no date yet. What to measure, and with what care

Checked on 21 September 2026 at 06:40 (Madrid time). The forecasts cited belong to the services that issue them and may have been updated since.

Anyone measuring rainfall or temperature in the Iberian Peninsula reaches the end of September with a practical question: should the summer campaigns close now and the autumn ones start? The official services say the heat continues and the first rain still has no date.

This week's signals

1. Full summer, with little rain until at least Friday 25th. For 21 to 27 September, AEMET expects temperatures clearly above normal across most of the Peninsula: from Tuesday, 32 to 34 °C over wide areas and up to 35 °C in southern Galicia, the Ebro depression, Extremadura and the Guadalquivir valley, with scarce precipitation, a pattern that will probably hold unchanged until at least Friday 25th. For mainland Portugal, the reference is IPMA. Source: AEMET, forecast for 21 September to 11 October (18/09/2026). What to measure: if summer campaign loggers are due to be collected on a calendar date, keep them logging while the episode lasts; the data, not the date, should mark the end of the campaign. With what care: check battery and free memory first, and note the new end date alongside the data.

2. After the 25th, no clear rainfall trend. For 28 September to 4 October, with greater uncertainty, AEMET again expects temperatures above the usual, especially in the north-east of the Peninsula, and warns that there is no clear trend for precipitation. For 5 to 11 October, with more uncertainty, it points to rainfall that is generally scarcer than usual on the Atlantic side. Source: AEMET, same forecast. What to measure: rainfall, with a rain gauge serviced during this dry week: funnel and filter clear of dust, leaves or debris, the unit level, a tipping bucket that moves without friction and the logger clock set correctly. With what care: if the funnel is blocked, water never reaches the bucket and the record shows zero, a zero that the series cannot tell apart from a dry day. Note the service date and, where the manufacturer provides for it, check the calibration with a known volume of water.

3. An autumn probably warmer than normal, and wetter in some areas. AEMET's seasonal forecast for September, October and November 2026 places temperatures in the upper tercile with high probability across Spain. For precipitation, it gives a higher probability of the upper tercile in the north-west of the Peninsula, the Mediterranean side and the Balearic Islands, of the lower tercile in the Canary Islands, and climatological probabilities elsewhere. Source: AEMET, seasonal forecast. What to measure: in the north-west, the Mediterranean side and the Balearics, a rain gauge ready before October; across Spain, temperature series that are not interrupted in autumn. With what care: a tercile is a probability for a three-month period and broad regions; it does not say when or where it will rain. For intense events, check your rain gauge's datasheet for the rainfall intensity up to which accuracy is stated.

4. In Europe, very extreme fire danger in France and the Pyrenees. In its 17 September update, EFFIS forecast very extreme conditions for 17 to 23 September across most of France and the Pyrenees, and extreme to very high danger over much of the Iberian Peninsula and the Balkans, against low danger across most of northern and central Europe. The burnt area in the EU stood at 669 118 ha for the year, less than on the same date in 2025 but above the 2006-2025 average of 346 567 ha. Source: EFFIS (JRC), current wildfire situation in Europe. What to measure: when the rain comes, its amount and time at your own point, with a logging interval that shows intensity and not just the daily total. With what care: the danger level is calculated by EFFIS and decisions belong to civil protection; your own record documents the site, it does not replace either.

Checklist

• Date and time of each consultation noted.
• Summer campaigns extended according to the data, with battery and memory checked.
• Rain gauge serviced: funnel clear, unit level, bucket free, clock correct.
• A rainfall logging interval that shows intensity.

Limits

This note is not an EIC Controls forecast: the forecasts are AEMET's and EFFIS's, with the dates given, and for Portugal it refers to IPMA. No forecast tables, maps or series are reproduced, and nothing above replaces official warnings.

References (consulted on 21/09/2026)

• AEMET (2026). Predicción para las semanas del 21 de septiembre al 11 de octubre de 2026: AEMET official blog.
• AEMET (2026). Predicción estacional septiembre-octubre-noviembre 2026: aemet.es.
• Joint Research Centre (2026). Current wildfire situation in Europe (EFFIS), updated 17/09/2026: link.
• IPMA (2026). Previsão para período alargado, Continente: ipma.pt.

Commercial selection by EIC Controls

The Rainfall (2m cable) Smart Sensor is a tipping bucket rain gauge with 0.2 mm resolution and a calibration accuracy of ±1.0% at up to 20 mm per hour; its datasheet states that it requires annual calibration, which can be done in the field or at the factory. It fits an autumn check such as the one this note describes. Still to be sized: the logger it connects to, the mounting point (it comes with a side bracket for post or tripod mounting and feet for surface mounting; if mounted away from the main tripod, the datasheet says to order it with a 6 m cable and an additional 1.5 m mast) and data communication.

View datasheet · Talk to a specialist