# Snow, hail and frost on the roof: where they matter, what to do afterwards and how to prevent damage

> How rare snow, hail and frost are in Portugal (IPMA normals), the weight of snow under the Eurocode, what hail does to tiles and solar panels, ice in the tile and what to do after an event.

- Page: https://telhadoseguro.pt/en/guides/snow-hail-ice-roof
- Language: English
- Updated: 2026-11-05

## Summary

- Outside the mountains, snow is rare: in the IPMA normals, Lisbon and Faro have no snow days and Penhas Douradas (1380 m) has about 25 a year. Hail is rare and very localised.
- The snow load comes from Eurocode 1 and the National Annex: three zones and a formula in which altitude counts squared. Only the designer calculates it for your house.
- Frost makes the tile flake. In cold areas, ask for the frost resistance class and good ventilation under the tile (APICER). On solar panels, hail can crack cells without breaking the glass.
- After snow or hail, do not climb onto the roof: photograph from the ground, tell the insurer within the policy deadline and have solar panels inspected.

Snow, hail and frost are not what damages roofs most in Portugal. But where they do happen, they damage in their own way: weight, blows and ice inside the tile. This guide says where these risks matter, what to do after an event and what we could not confirm.

*Updated on 4 November 2026. General information. It is not a structural calculation: only the designer can determine the snow load of a house.*

## The essentials

- **Snow is rare outside the mountains.** In the IPMA normals, Lisbon and Faro have no snow days and Penhas Douradas (1380 m) has about 25 a year.
- **Hail is rare and does not pick a zone.** It falls on the coast and inland, in very localised showers.
- **Frost damages the tile from the inside.** In cold areas, ask for the frost resistance class.
- **After an event, do not climb onto the roof.** Photograph from the ground and tell the insurer.
- **Works in a high area: ask the designer for the snow load.**

## How rare are these events?

The IPMA publishes the average number of days a year with snow and hail in the 1971 to 2000 normals and, for frost, in the 1991 to 2020 ones (days with a minimum temperature below 0 °C):

| Station (altitude) | Snow days | Hail days | Frost days |
|---|---|---|---|
| Penhas Douradas (1380 m) | 24.9 | 2.0 | 54.4 |
| Montalegre (1005 m) | 18.5 | 2.5 | 41.3 |
| Guarda (about 1000 m) | 11.7 | 1.6 | 31.9 |
| Bragança (690 m) | 6.1 | 1.2 | 53.4 |
| Vila Real (480 to 560 m) | 1.4 | 3.4 | 16.7 |
| Porto, Pedras Rubras (70 m) | 0.2 | 4.6 | 1.4 |
| Lisbon (77 m) | 0.0 | 1.5 | 0.0 |
| Faro (a few metres) | 0.0 | 1.1 | 0.0 |

The number of days does not tell the size of the stones. And the IPMA explains that hail is recorded by eye, only at classic stations, fewer and fewer, so these numbers fall short.

## Snow: the weight on the roof

Buildings are designed with Eurocode 1, part 1-3 (NP EN 1991-1-3), and its National Annex. We did not find the annex freely available. We read a lecture note from Instituto Superior Técnico (2011) that summarises it. According to it:

- the country has **three snow zones**, Z1, Z2 and Z3. On the note's map, Z1 covers the interior of the centre and the north-east; the south and the islands are in Z3;
- ground snow, in kN/m², is **sk = Cz × [1 + (H/500)²]**, with H the altitude in metres and Cz equal to 0.30 (Z1), 0.20 (Z2) and 0.10 (Z3), for a 50-year return period. The load on the roof also depends on its shape and on the wind;
- in Z1 an exceptional snow drift on the roof is also considered. In Aguiar da Beira, Fornos de Algodres, Mangualde, Nelas, Penalva do Castelo, Sátão and Viseu, an exceptional snowfall also counts, with ground snow multiplied by 2.5.

**Altitude counts squared.** In the formula, altitude enters squared: going higher raises the snow load on the ground a lot. Your municipality's zone is on the national annex map, which we did not see.

By the sea, snow hardly enters the calculations. In the Serra da Estrela, in Montalegre or in Bragança, a new or replaced roof should be calculated with it. Slope matters too: the APICER guide says snow calls for steeper slopes, to avoid overloads. See the [minimum slope](https://telhadoseguro.pt/en/guides/minimum-roof-slope).

In a snow warning (28 February 2025, for snow above 1200 to 1400 m), Civil Protection asks people to unblock drains, secure loose structures and avoid travelling. It does not mention clearing snow from roofs.

## Hail: tiles, skylights and panels

In the classic stations, hail is most frequent between February and April. On 30 and 31 May 2020, the IPMA confirmed by radar hail in Guarda, Fundão and Castelo Branco, among other municipalities, with orange and red warnings. On 12 June 2023, there was hail in Beira Alta and Trás-os-Montes, in some cases lasting tens of minutes.

**Tiles.** We found no hail tests on Portuguese tiles. In a Swiss study (2007), clay tiles are among the most resistant materials for watertightness. The ice-ball test, from 10 to 50 mm, gives five classes, and the study's flat clay tiles sit in class 4 (40 mm). The study separates cosmetic damage (chips) from functional damage (broken tile, water getting in).

**Solar panels.** The US Department of Energy (FEMP) says the basic IEC 61215 test uses 25 mm ice at 23 m/s and is not enough for severe hail. It advises front glass of at least 3.2 mm and warns that hail can crack cells without breaking the glass. See [solar panels](https://telhadoseguro.pt/en/guides/solar-panels-on-roof-what-to-check) and [skylights](https://telhadoseguro.pt/en/guides/skylights-roof-windows), for which we found no data.

## Frost and ice

When the water inside a tile freezes, the tile flakes. The APICER and CTCV guide (2018) says to replace a tile that flakes and, as prevention, to **ventilate the underside well** and use tiles with proven frost resistance and low absorption. Since 2017, clay tiles for outdoor use have classes 1 to 3, from 30 to 150 or more freeze-thaw cycles. The table is in [tiles and climate](https://telhadoseguro.pt/en/guides/roof-tiles-by-climate).

**Ice at the eaves.** A US university explains it like this: heat from the house melts the snow, the water runs to the cold eave and freezes, forming a dam. The causes are poor insulation, warm air leaking into the attic and weak ventilation. It comes from much colder climates and **we found no Portuguese data**. According to the source, the fix is to seal and insulate. See [insulation](https://telhadoseguro.pt/en/guides/roof-insulation) and [gutter cleaning](https://telhadoseguro.pt/en/roof-cleaning/gutters), which the ANEPC asks to keep clear.

## After hail or snow

1. **Do not climb.** Snow and ice are slippery: see [work at height](https://telhadoseguro.pt/en/guides/work-at-height-roof).
2. **Do not stand under the eaves**: loose tiles, snow or ice may fall.
3. **Photograph from the ground**, with the date, before touching anything. See the [first 48 hours](https://telhadoseguro.pt/en/guides/damaged-roof-first-48-hours).
4. **Tell the insurer** within the policy deadline. Look in it for "hail", "snow" and "weight of snow". See [storm insurance](https://telhadoseguro.pt/en/guides/home-insurance-storm-roof).
5. **If the ceiling creaks or sags under heavy snow** (our suggestion), leave the room and call an engineer; in danger, 112.
6. **Solar panels:** switch the system off until inspected. FEMP asks for an inspection within a month.

## What the contractor should check

Our suggestion, based on the sources above: broken, chipped or displaced tiles; dented flashings, joints, skylights and gutters; ventilation under the tile and insulation, if there is ice or condensation; fixing, glass and connections of the panels. Ask in writing what is new damage and what was already there, because of the insurance. See how to [choose a contractor](https://telhadoseguro.pt/en/guides/choosing-a-roofing-contractor).

**See also:** On the structure that holds the covering, see [timber, concrete and steel](https://telhadoseguro.pt/en/guides/roof-structure-timber-concrete-steel).

## What we could not confirm

- **The text of the National Annex.** We read only the 2011 lecture note. There is a 2017 amendment (A1) we did not read, which may change values. The map does not show the zone of each municipality.
- **The snow zone of your parish.** Ask the designer.
- **How much hail falls in each region:** there are only days observed by eye.
- **Whether your insurance covers snow or hail.** It depends on the policy.
- **Hail tests on Portuguese tiles and skylights**, and **ice at the eaves in Portugal.**
- **The EN 1304 and EN 539-2 standards:** they are sold and we did not read them.

## Sources (read on 4 November 2026)

- IPMA, [normals 1971-2000](https://www.ipma.pt/bin/file.data/climate-normal/cn_71-00_PENHAS_DOURADAS.pdf) (Penhas Douradas; the other stations have the same address) and [normals 1991-2020](https://www.ipma.pt/bin/file.data/climate-normal/cn_91-20_PENHAS_DOURADAS.pdf).
- IPMA, [hail on 30 and 31 May 2020](https://www.ipma.pt/resources.www/docs/publicacoes.site/Rel_granizo_30e31MAI2020_vf.pdf), November 2020.
- IPMA, [hail and heavy rain in Beira Alta and Trás-os-Montes](https://www.ipma.pt/pt/media/noticias/documentos/2023/Noticia_Granizo_TMontes_jun2023_NL.pdf), 16 June 2023.
- P. Mendes (IST), [Quantification of actions on buildings according to Eurocode 1](https://scholar.tecnico.ulisboa.pt/api/records/bc5785d2-2528-4353-99f6-7492e4a5a323/file/225e03ae3e5f90fffd2ae74de2518b53464789cc574583ce07f7440f4ff88eaa.pdf), April 2011 (in Portuguese; not the official annex).
- ANEPC, [Notice no. 5/DCS/2025](https://prociv.gov.pt/media/vt4luvlg/aviso-à-população-_-precipitação_e_queda-de-neve-_-medidas-preventivas_28fev.pdf), 28 February 2025.
- APICER and CTCV, [Guide for the Design and Application of Ceramic Roof Tiles](https://www.apicer.pt/apicer/media/5c06bd0e8d436.pdf), 2018.
- Commission Delegated Regulation (EU) 2017/1475, [text](https://www.legislation.gov.uk/eur/2017/1475/annexes/2017-01-26/data.xht) and [APCMC note](https://apcmc.pt/legislacao/telhas-ceramica-uso-exterior-resistencia-ao-gelo/).
- Präventionsstiftung der kantonalen Gebäudeversicherungen (Switzerland), [Elementarschutzregister Hagel](https://cms.vkg.ch/media/g4yhbbas/hagel_d.pdf), 2007 (in German).
- U.S. Department of Energy, FEMP, [Hail Damage Mitigation for PV Systems](https://www.energy.gov/femp/hail-damage-mitigation-solar-photovoltaic-systems) (no visible date).
- M. Dries and R. Seavey, University of Minnesota, [Ice Dam Symptoms and Solutions](https://conservancy.umn.edu/server/api/core/bitstreams/45d32107-79c4-4dae-9467-b49cdd392139/content) (data from 2015-2016).
- Dlubal, [snow according to NP EN 1991-1-3](https://www.dlubal.com/pt/zonas-de-carga-para-neve-vento-e-sismos/neve-np-en-1991-1-3.html), only for the A1:2017 amendment (not official).

## FAQ

### In which parts of Portugal does snow matter for the roof?

Mainly in the mountains and the high interior. In the IPMA normals (1971 to 2000), Penhas Douradas (1380 m) has 24.9 snow days a year, Montalegre 18.5, Guarda 11.7 and Bragança 6.1. Lisbon and Faro have 0.0. For your house's snow load, ask the designer for the zone.

### How is the snow load on a roof calculated?

According to a lecture note from Instituto Superior Técnico (2011) on the National Annex, ground snow is sk = Cz × [1 + (H/500)²], with Cz of 0.30, 0.20 or 0.10 depending on the zone. Then the roof shape and the wind come in. We did not read the official annex: the calculation is the designer's.

### Does hail damage tiles and solar panels?

It can. In a Swiss study (2007), clay tiles are among the most resistant materials for watertightness, but we found no tests on Portuguese tiles. The US Department of Energy warns that hail can crack solar cells without breaking the glass.

### Can frost damage my tiles?

Yes, in cold areas. Water inside the tile freezes and the tile flakes. The APICER says to replace a tile that flakes and to ventilate the underside well. Ask for the frost resistance class (1, 2 or 3), which has existed since 2017 for clay tiles.

### What should I do after hail or snow?

Do not climb onto the roof or stand under the eaves. Photograph the damage from the ground, with the date, and tell the insurer within the policy deadline, looking in the policy for the words hail and snow. If you have solar panels, switch the system off until inspected. In danger, call 112.

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Source: https://telhadoseguro.pt/en/guides/snow-hail-ice-roof. Independent information, not legal or tax advice.