Image: UbisoftOfficial screenshot from Ubisoft.
Stay Cool asks you to finish any Special Operation without the PG-240X going over 50% on its temperature meter. It is all about keeping the canister in shade and water.
1. Talk to Lola and pick any Special Operation on Standard. 2. Clear the soldiers along your route before you touch the canister. 3. Carry the PG-240X from shade to shade, cooling it in water when you can. 4. Reach extraction with the meter never past half.
Plan the route before you pick it up, since stopping to fight in the sun is what pushes the meter up. Shoot holes in water barrels to cool it on the move. In co-op, one player clears ahead while the other carries.