Start with a light base
A T-shirt with trousers, a shirt with jeans, a midi dress, or a top with a skirt will suit many mild days. Choose fabric weight based on humidity and wind rather than temperature alone.
If you tend to feel cold, keep your arms covered with a fine knit or long-sleeved shirt. If you run warm, use an open overshirt or carry the layer instead.
Add one adaptable layer
A cardigan, denim jacket, unlined blazer, chore jacket, or lightweight trench handles most temperature shifts. It should fit over the base without making the outfit feel tight.
For rain or strong wind, swap style-first outerwear for a practical shell. Weather protection is easier to integrate when the rest of the outfit stays simple.
Match shoes to the day
Sneakers, loafers, flats, and ankle boots can all work at 20°C. Sandals make sense when the forecast is dry and the day stays warm; closed shoes are usually easier for long walks or cool evenings.
Check the hourly forecast before leaving. The difference between the morning low and afternoon high often matters more than the headline temperature.