The temporary wind tunnel, which uses two industrial fans, aims to help women beat 'gale fail' when a gust of wind lifts their dress or skirt to reveal their underwear.
The in-store fans can be adjusted to mimic a light breeze or 40mph gale-force winds.
Customers will be able to book a session with a stylist who will advise them on which outfits will be the most windproof. The activation will be available from 23 May to 25 May.
The wind-test brand experience was produced in-house and trialled earlier this week in the Oxford Street store's window.
Alain Mehada, head of personal styling at Debenhams Oxford St, said: "It can ruin a special day when someone has spent a long time choosing what to wear, only to find themselves battling with the wind, holding on to their hat with one hand and the hem of their skirt with the other, while teetering in skyscraper heels.
"A big part of many summer events, particularly weddings and big race meetings such as Ascot, is wearing a special outfit that makes you feel confident that you look your best, but relaxed enough to enjoy the day. It is very difficult to do that if you are worried about your dress flying up to reveal more than you bargained for, or your lovely new hat soaring off into the distance."
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