The 45-degree uniform: dressing for peak shoulder season
Forty-five degrees is the Bermuda Triangle of getting dressed. Your winter coat is too much by noon, your fall jacket is too little at 8am, and the forecast's "high of 52" tells you nothing about the wind cutting across the platform. Shoulder season demands a system, not a jacket: a uniform of interchangeable layers that handles the full swing of a 45-degree day.
The formula: three light layers, no heavy ones
The mistake is reaching for one warm layer. Three light layers trap more warm air than one heavy one, and they come off one at a time as the day warms. The uniform: a breathable base (merino or a technical long-sleeve, not cotton), a mid-layer with a zip neck for venting, and a wind-resistant shell. At 8am you wear all three; by 2pm the shell is tied around your waist and the mid-layer is unzipped. No outfit change, no suffering.
The shell is the most important piece and the most misunderstood. At 45 degrees you do not need insulation from your outer layer; you need wind blocking. Wind is what makes 45 feel like 35, and a wind-resistant shell over a warm mid-layer outperforms a heavy coat with no wind protection. Look for a shell that packs into its own pocket, because you will be carrying it by afternoon.
The bottom half
Legs are simpler: one substantial layer. Full-length trousers in a dense weave, or jeans with tights underneath on windy days. The ankle gap is the enemy; cropped trousers with bare ankles at 45 degrees undo everything the top half accomplishes. Socks matter more than people think: a mid-weight sock in a closed shoe beats a heavy boot with thin socks, because warm feet change how the whole body perceives the temperature.
Accessories do the fine-tuning
A light beanie or headband, thin gloves, and a scarf you can stuff in a pocket are the thermostat of the uniform. Mornings get all three; afternoons get none. This is the cheapest part of the system and the highest-leverage: extremities drive perceived warmth, and being able to add or remove a hat is the difference between comfortable and cranky. Keep the set in the shell's pocket so it is always with the uniform.
What not to wear
Skip the heavy winter coat: you will overheat by midday, carry it all afternoon, and learn nothing. Skip the bare-leg-plus-boots look until it is genuinely warmer; 45 degrees punishes it. And skip cotton as a base layer, because the morning chill plus any exertion leaves cotton damp, and damp cotton at 45 degrees is the coldest fabric there is. The uniform works because every piece earns its place. At the hardest temperature of the year, that is the only strategy that does.