Here are a few "transitional" spring outfit ideas by weather type and temperature:
Rainy, 45 degrees:
-Stick to a light cardigan or v-neck shirt under raincoat to avoid bulk.
-Wear skinny jeans so that it's easier to slip on wellies.
-A 3/4-length sleeved jacket will feel lighter on a cool spring day.
-Flats are perfect for spring...you're not showing toe quite yet, and you can wear them without socks.
Sunny, 55 degrees:
-Layer lightweight, t-shirt materials over each other...cotton cardigan + cotton t-shirt.