Weather for March????

[daffidyll]

Hi, We'll be going to Disneyland the 2nd week of March and Vegas the 3rd week. We are coming from hot and humid summer weather conditions so have NO idea how to pack for this trip. Can anyone tell me what the weather is typically like in Vegas in late March? Does anyone know if it is vastly different to the weather at DL? Should I be packing more or pants/long sleeves OR shorts/short sleeves....will we need warm coats (sadly we don't even own any as it never gets really cold here) or just light weight sweaters/jackets? Many thanks!