Frustrated toddlers

Any other moms dealing with their toddlers who are getting frustrated and hitting? Hitting parents, the wall or furniture or even the dog? My son just started doing this the past couple of weeks. At first we thought it was funny but now we are trying to put our foot down and try to teach him to feel his feelings without hitting. However he has a speech delay so communication is hard. We try to remain calm, teaching him gentle (which he knows) and just getting on his level .

Anyone have advice? I believe what he is going through is normal, he doesn’t go to daycare and is an only child until September. Then his baby sister arrives.