fb prophet regressor underestimated

Question

I am working on monthly sales data. especially in the month of June, the sales are almost 3*X. how do I add a regressor? I tried to create a binary regressor but the value is still underestimated. how can I increase the impact of the regressor?

def main_season(ds):
    date = pd.to_datetime(ds)
    if date.month > 3 and date.month < 7:
        return 1
    else:
        return 0
X_tr['main_season'] = X_tr['ds'].apply(main_season)

def peak_season(ds):
    date = pd.to_datetime(ds)
    if date.month == 6:
        return 1
    else:
        return 0
X_tr['peak_season'] = X_tr['ds'].apply(peak_season)