In WA, a misdemeanor carries a maximum possible punishment of 90 days in jail and $1000 fines.
Depending on the court and the defendant, a first time convict likely will not be in jail the whole 90 days. The court may impose the full sentence but suspend most of the sentence if the convict meets the conditions of the court.
You may want to review your facts and options with an attorney. You should not discuss the details of your case with anyone but your attorneys.
One possible outcome is that your attorney can get the case dismissed. There are many reasons why a case will be dismissed. With a dismissal, there is no conviction and no sentencing.
Another possible outcome is some sort of agreement can be reached with the prosecutor. Perhaps the defendant will have to attend some classes, pay some court fees, stay out of legal troubles for a certain time; upon the defendant meeting the terms of the agreement, the prosecutor will dismiss the case.
The maximum you could serve is one year in jail and/or a $5000 fine. However, with no criminal history, it is unlikely that you are facing the maximum. Usually, the lawyer handling your case can give you a better sense of what your particular judge will sentence. Since the judge has discretion, the sentences vary from court to court.
If you are charged with RCW 9A.36.041 (Assault in the fourth degree), that is a gross misdemeanor. A gross misdemeanor does carry a maximum penalty of 1 year in jail and $5000 fines.
So, you should check how are charged: a misdemeanor or a gross misdemeanor. Perhaps you are being charged by a city that defines a lower penalty.