What is common to wear on the coast during April 21-28th? I know temperatures can vary, but what is common attire during this time frame? Are women still wearing warmer clothing or sun dresses? Sandles? I am sure too cold to swim, but do others go to beach to relax in the sun? Thanks much. We are staying in Sant'Agata and Amalfi.
Historic averages are hi temp in low 70s and lows upper 50s
Someone coming from Phoenix where it likely in 80s ( or more) at that time of year is not the same as coming from a northern area where high may be in the 50s.
What the locals are wearing is irrelevant. Wear what you find comfortable for the conditions
You'll want layers. It could be very chilly, or warm or (unlikely) hot. It may rain. Here is the Weather Underground page for Amalfi.
https://www.wunderground.com/weather/it/amalfi
If you click the HISTORY tab in the row near the top, you can look up past years' weather for your dates in April.
A medium-weight dress with sleeves or a pair of medium-weight pants or jeans with a blouse could be your base, and then add a sweater or shawl, a windbreaker and hat, tights or socks. Oh, and a silk undershirt (my secret weapon). If you're a sandals wearer unless it's literally freezing (32F) then bring sandals, otherwise shoes or ankle boots are probably better. If you're the type who'll enjoy the beach when it's, say, 55 or 60F, go for it.
My favorite site for comprehensive weather is weatherspark.com.
It will give you, among other things, humidity information. That may help as much as knowing ambient temperature averages.
I use it for all my travel planning.