everyone is different, and eevery day is different.
1, check the weather EVERY morning before getting dressed
2. carry hats and magic (stretchy) gloves if you will be out late
3. If someone is really worried, have them wear hiking pants that zip off at the knee, so they have shorts and pants!
4. carry a lined hoodie for everyone.
We have done january and february in mostly shorts and tees, with a fleece or hoodie for morning..Then the next day, it was 78 and we went swimming, followed by a day that was wet and cold, and we did jeans and sweatshirts and fleece and gloves!
Unpredictable. We made sure to check the weather, and carry a bag with the gloves and hoodies, and it all worked out.