A short rule of thumb
Dress for the summit as if you were going to the top of a 300-metre hill in the same park. In practice that means an extra layer in winter and an extra wind-breaker whenever the forecast wind at summit level exceeds 40 km/h.
By season
Winter (December – February)
A warm jacket, a scarf, and, on days with wind over 30 km/h, a hat. The waiting area in the lift corridor is heated; the summit platform is not. On a sunset climb, allow for standing fifteen minutes in direct wind.
Spring (March – May)
A medium jacket. Spring showers can be sharp; a light hooded shell is more useful than a long coat.
Summer (June – August)
The summit is noticeably cooler than the ground. A long-sleeved shirt or a light jumper is usually enough. On the hottest days, the summit platform catches a welcome breeze — the only shade in central Paris at that height — and the climb is a relief rather than a chore.
Autumn (September – November)
Autumn is the trickiest season to dress for. Mornings can be chilly, afternoons can be mild. We tend to layer: a long-sleeved shirt, a cardigan or soft jacket, and a light shell in a bag.
Footwear
Steps are unavoidable even if you take the lift — the queue zig-zags, and the esplanade around the base of the tower is uneven stone. Walkable shoes are better than new leather shoes. The platforms are flat and even, but the stairs between the second floor and the summit (for those who choose to climb them) are open to the wind and should be done in shoes you can trust.
Pockets
The deck is open and the metal rails are higher than waist height, but a phone or a small camera can still slip over the edge if dropped near the railing. If you are photographing, a strap is helpful. For headphones and small items we recommend inside pockets, not back pockets.
Children
Children feel the cooler summit air a touch earlier than adults. An extra layer in a backpack is a safe habit, especially for a late-afternoon climb that ends after sunset.