Long johns or warm underwear aren't necessary in 40-degree temperatures. Wearing jeans or formal slacks will keep your legs warm enough. Unless you wear leggings or tights beneath, you should avoid wearing shorts. The heat will just rise through the fabric of the shorts and feel like it's coming from inside your body. Warm jackets are useful for 48-degree days. A fleece or wool jacket is good protection against wind and cold. Avoid cotton unless it's treated with chemicals to repel insects. If you have a choice, choose natural fibers over synthetics. Shoes are important when it comes to keeping cool in hot climates. Heels can add up to five times your body weight to your load on your feet, so consider the type of shoe you're wearing. If you need to walk a lot, look for shoes with thick soles that offer some protection from the ground while still allowing your feet to breathe. In conclusion, dress comfortably but appropriately for the weather. Long sleeves and pants are best because they cover more area of skin, which keeps you cooler. Jeans aren't recommended because you can't easily replace them if they get torn or dirty. Also, avoid cotton because it's not as effective at keeping you cool as other materials.