Some people say you paint in summer, others paint in any month. This guide puts together two things we found: the temperature and humidity limits on technical data sheets, and IPMA’s climate normals for Lisbon, Porto and Faro. It does not name a “best month”, because no source does. It shows what the numbers allow us to conclude. The 5 °C and 80% humidity limits already appear in preparing the home for painting. Here we add the other limits and the climate.
Updated 4 November 2026. General information, not a substitute for a technician’s assessment.
The essentials
- Nearly every sheet asks for air above 5 °C and relative humidity below 80%. Heat limits vary: 25 °C for a silicate paint, 30 °C for lime and textured coatings, 35 °C for one emulsion paint.
- Outdoors the main risk is rain during drying: from 12 hours for a textured coating to 7 days for an elastomeric paint.
- Indoors, temperature is rarely the problem. Humidity and cold walls matter more, and they link to condensation.
- In IPMA’s normals, June to August have the fewest rain days at all three stations. July and August come close to the heat limits.
- Averages are not a forecast. Check the weather for your working days.
Limits set by the sheets
| Product | Air | Relative humidity | Other limits |
|---|---|---|---|
| Wall paints, CIN and Barbot (several) | > 5 °C | < 80% | surface 2 to 3 °C above the dew point |
| Cinoflex (exterior) | > 5 °C | < 80% | no direct sun, no rain expected while drying |
| Dyrustar (Dyrup) | 10 to 35 °C | < 80% | avoid rain, fog and wind |
| Aqua Primer (CIN) | > 10 °C | < 80% | below 10 °C with RH > 80%, stain sealing is reduced |
| Sintecin (synthetic enamel) | > 5 °C | < 75% | wood at 8 to 12% moisture |
| Dissoltin (silicate) | 5 to 25 °C | < 80% | no rain in the following days |
| Com-Cal (lime) | 5 to 30 °C | not stated | prohibition icons on the sheet that we could not read |
| Fassa C 285, weber.plast decor | 5 to 30 °C | not stated | protect from rain, fog and wind |
Drying: what cold and damp do
The sheets give times at 20 or 23 °C. CIN warns that low temperature with high humidity lengthens drying. Examples we read: recoat after 3 to 4 hours for a wall paint and 4 hours for Barbomat (at 23 °C and 55%), 16 to 24 hours for the synthetic enamel, 24 hours for Cinoflex and 7 days to full dryness for Fassa at 20 °C. Vinylmatt asks for 28 days before washing. The further from those conditions, the less reliable these numbers are.
The climate, according to IPMA
Normals 1991-2020. Days with 1 mm of precipitation or more:
| Month | Lisbon | Porto | Faro |
|---|---|---|---|
| January | 10.0 | 12.8 | 6.0 |
| February | 7.9 | 10.0 | 5.4 |
| March | 7.6 | 9.9 | 5.6 |
| April | 7.9 | 10.4 | 5.3 |
| May | 5.8 | 8.9 | 3.8 |
| June | 2.0 | 4.9 | 0.8 |
| July | 0.6 | 3.1 | 0.2 |
| August | 1.1 | 3.2 | 0.2 |
| September | 3.8 | 5.8 | 1.9 |
| October | 8.7 | 11.1 | 6.0 |
| November | 9.9 | 13.0 | 6.6 |
| December | 10.0 | 12.4 | 7.0 |
Annual rainfall: 793.5 mm in Lisbon (Geofísico), 1146.9 mm in Porto (Pedras Rubras), 455.1 mm in Faro. The wettest months are November (133.9 mm in Lisbon, 165.9 mm in Porto) and December (90.0 mm in Faro).
Temperature: the mean daily maximum in July and August is 28.2 and 28.8 °C in Lisbon, 24.3 and 24.8 °C in Porto, 29.4 and 29.2 °C in Faro. Days with a maximum of 30 °C or more number 33.2 a year in Lisbon, 13.0 in Porto and 35.5 in Faro, peaking in July and August (8.5 and 10.2 in Lisbon, 13.1 and 12.4 in Faro). The mean daily minimum in January is 8.6 °C in Lisbon, 6.4 °C in Porto and 8.3 °C in Faro. Of the three, only Porto has frost days: 1.4 a year.
Indoors and outdoors
Indoors. Mean minimums stay above 5 °C in every month. But averages hide cold nights and cold walls, and the normals do not include relative humidity. The sheets ask for relative humidity below 80%, inside the home too. If the wall has mould or condensation, the season is not the problem: see mould on walls.
Outdoors. Rain, sun and wind add up. The sheets forbid applying onto a sunlit surface, and the textured coating needs 12 hours without rain. For the paint, see which paint for the facade. For council and condominium rules, see painting the facade.
What the numbers allow us to say
Our reading, not a recommendation from the sources. Outdoors, the months with least rain are also the hottest. May, June and September sit between the two extremes: less rain than winter and fewer days above 30 °C than July and August. In July and August, start on the shaded side. In winter, rain and cold lengthen drying. In every case the forecast for your working days decides, not the month.
Step list
- Read the air, humidity, dew point and rain limits on your paint’s sheet.
- Outdoors, check the forecast for the application and the drying (12 hours to 7 days, depending on the sheet).
- Indoors, ventilate and avoid days of fog or persistent rain.
- If you cannot meet the limits, wait. Work out litres with the calculator.
What we could not confirm
- Monthly relative humidity. The normals we read do not include it.
- Wall temperature in the sun. No source.
- Stations in other areas. We read only Lisbon, Porto and Faro.
- Painter prices or availability by season.
- What “foreseeable rain” means. The sheets do not say. We took it as the application and drying days.
- Lime and silicate: the Com-Cal sheet has pictograms we did not read.
Sources (read on 4 November 2026)
- IPMA, Climate Normals 1991-2020: Lisboa/Instituto Geofísico (535), Porto/Pedras Rubras (545) and Faro (554), version 1.0 of 2024.
- CIN, Cinoflex 10-760, Vinylmatt 10-250 (rev. July 2026), Aqua Primer 12-830 (February 2020) and Sintecin Satinado 48-261 (December 2016, reseller copy).
- Barbot, 1302 Barbomat (Rev. 15) and 1300 Barbocril Plus D10 (Rev. 11).
- PPG Dyrup, Dyrustar ITC 839, December 2017 (reseller copy).
- Dissoltin, Tinta de Silicato FT102.04, January 2023. Com-Cal, Tinta de Cal para Exteriores, 26/04/2024.
- Fassa Bortolo, C 285 BETON-E, 05/2026. Weber, weber.plast decor M/F, 2018 (reseller copy). Secil, Isovit Rev Reflect.