Windows and heavy rain in Spain: how to stop leaks

Why DANA storms test your windows

On the Costa Blanca, in Torrevieja and the Vega Baja, autumn is DANA season. A DANA is an isolated pocket of cold air high in the atmosphere, and it can drop more than 100 litres per square metre in a few hours. In early October 2026 AEMET, the Spanish weather service, warned of very heavy rain in eastern Spain, and by mid-month it was watching another DANA. For your windows, the problem is not only the amount of water. It is rain driven sideways by the wind, which hits the frames under pressure and finds any open joint.

A window that copes with ordinary rain all year can still drip during a DANA. That does not always mean it is broken. Often the water comes in through a blocked drain slot or cracked sealant.

Where the water gets in: the 5 usual spots

• Blocked drain slots. Windows, and especially sliding doors, have small slots at the bottom of the frame that let water out. If they fill with sand, dust or insects, water builds up in the track and spills inwards.
• The joint between frame and wall. The sealant or foam used when the window was fitted ages in the sun and cracks. Water runs behind the frame and shows up on the wall or under the sill, even if the window itself is fine.
• Shutter box and guides. A badly sealed roller-shutter box or a loose inspection cover lets in water and air. It is a classic weak point in older roller shutters.
• Worn rubber gaskets. Over the years gaskets harden and stop pressing against the sash. On tilt-and-turn windows you see drops at the bottom of the sash.
• The terrace door threshold. Balcony doors and sliders with a very low threshold are more sensitive. If water pools on the terrace and has nowhere to go, it can rise over the bottom profile.

What to check before the storm (15 minutes)

1. Clean the drain slots. Open the sash, vacuum the track and push a thin wire or a cocktail stick through the slots. Pour a glass of water into the track: it should drain outside within seconds.
2. Look at the outside sealant around the frame. If it is cracked, peeling or missing, renew it with an exterior-grade sealant on a clean, dry surface.
3. Close every sash properly and make sure the handle turns all the way. A tilt-and-turn window that is not fully closed does not press on its gaskets.
4. Clear the terrace or balcony drain. Leaves and sand block it and the water rises to the door.
5. Lower the shutters on the side facing the wind. They stop part of the rain before it reaches the glass.
6. Keep towels or a draught excluder ready for the terrace door threshold in case water collects.

If you live abroad part of the year, ask a neighbour or your property manager to do this check and to send you a photo after the storm.

During and after the rain

If you see water, take a photo or a short video of exactly where it appears: the bottom corner of the sash, under the sill, on the wall next to the frame or from the shutter box. For whoever repairs the window, that photo is worth more than any description. Dry the area quickly to avoid damp stains and mould.

Safety comes first: follow AEMET and Civil Protection warnings, do not go down to garages or basements during the storm and stay away from dry riverbeds (ramblas).

Repair or replace?

Many leaks can be fixed without replacing anything: cleaning drain slots, new gaskets, adjusting the hardware or resealing around the frame. But in some cases a repair is expensive and does not last:

• Old aluminium sliders without a thermal break and with an open track, which drip every time it rains with wind.
• Warped frames or rotten wood, where the gasket can no longer seal.
• Leaks that come back in the same place after several repairs.
• Besides water, you also notice draughts, condensation in winter or street noise.

A new window is made and fitted as a system: a profile with calculated drainage, a double gasket, an outside sill and perimeter sealing done with exterior materials. A window's resistance to driving rain is tested in a laboratory to the European standard EN 12208 and shown in its CE marking: the higher the class, the more water and wind pressure it withstands without leaking.

If you are choosing a material, PVC with double gaskets is usually the most watertight option for the price. Thermally broken aluminium is ideal for large sliders and dark colours. On exposed terraces a glass curtain keeps the wind out but is not watertight: some water gets through the joints between the panes.

How we can help

• Send us a photo or video of the leak on WhatsApp and we will tell you whether it can be repaired or should be replaced.
• We make the windows in our own workshop in San Fulgencio and fit them with our own team in Torrevieja, Rojales, Guardamar, Orihuela Costa and across the Costa Blanca. We speak English.
• Get an estimated price online in a minute, and read our guide to replacing windows in Spain if you are a foreign homeowner.

Sources

• AEMET: current weather warnings.
• Artículo 14 (14/10/2026): AEMET watching a possible DANA with heavy rain (in Spanish).