40°F is prime running weather once you're moving. a long sleeve and tights cover it for most people, with light gloves you can stash once your hands warm up. dress like it's 50°F — you generate a lot of heat on the run.

Long sleeve Micromesh with reflective stitching.
Bandit Micromesh Reflecto Stitch LS Tee →

100% Superfine Merino Wool liner gloves from Japan.
Satisfy CloudMerino Liner Gloves →
Stamina fabric scoop neck bra. Three pockets, all-ways stretch support.
Bandit Stamina Scoop Neck Run Bra →
Breathable Micromesh long sleeve for cool runs.
Bandit Women's Micromesh Long Sleeve Tee →
Stamina-V fabric with 37.5 thermoregulation. Unlined, five-pocket system.
Bandit Stamina-V High Waist Legging →
100% Superfine Merino Wool liner gloves from Japan.
Satisfy CloudMerino Liner Gloves →between 7°C and 18°C is the transitional band: a long sleeve up top with shorts or half tights below. it's the range where a top layer and bare legs often beats the reverse, since your core cools slower than your legs.