How to change the font.size for all subplots with sns.set and rcParams

I'm trying to change all font elements in a series of boxplots I'm plotting. My code is similar to

from pathlib import Path
import numpy as np
import pandas as pd
import seaborn as sns
import matplotlib.pyplot as plt


def plot_group(df, nrow, ncol, size, plot_title):

    sns.set(style="darkgrid")
    plt.rcParams['font.size'] = size
    fig, axes = plt.subplots(nrow, ncol, figsize=(15, 10), tight_layout=True)
    fig.suptitle(plot_title)
    n_boxplots = 2
    for i in range(nrow):  
        for j in range(ncol): 
            current_ax = axes[i, j]
            sns.boxplot(data=df[['foo','bar']], palette="Set2", ax=current_ax)
            current_ax.set_title("foo", fontsize=18)

    plt.savefig(f'font_size_{size}.png', dpi=75)
    plt.close(fig)

nrow = 3
ncol = 3
rng = np.random.default_rng(0)
arr = rng.random((30, 2))
df = pd.DataFrame(data=arr, columns=['foo', 'bar'])
for size in [14, 22]:

    plot_title = f"Font size = {size}"
    plot_group(df, nrow, ncol, size, plot_title)

However, this results in two figures where only the suptitle font size changes, but everything else stays the same:

Why? How can I fix this?

• There are many answers dealing with sns.set, sns.set_style, and rcParams.
  • seaborn rc parameters for set_context and set_style
  • Seaborn cannot override grid.linewidth
• As shown in the seaborn rcmod.py file, rcParms are already being set by the seaborn functions.
• .set is an alias for .set_theme
• Override rcParams set by .set_theme using the parameters as defined here.
  • There are _context_keys and _style_keys.
• In the case of this code, remove sns.set(style="darkgrid") and plt.rcParams['font.size'] = size, and use sns.set_theme(context={'font.size': size}) instead.
  • Using rcParams directly, when using sns.set_theme, does not seem to work.
• Tested in python 3.11.2, matplotlib 3.7.1, seaborn 0.12.2

def plot_group(df, nrow, ncol, size, plot_title):

    sns.set_theme(context={'font.size': size})  # use set_theme
    
    fig, axes = plt.subplots(nrow, ncol, figsize=(15, 10))
    axes = axes.flat
    fig.suptitle(plot_title)
    for ax in axes:
        sns.boxplot(data=df, palette="Set2", ax=ax)
        ax.set_title("foo", fontsize=18)

    plt.savefig(f'font_size_{size}.png', dpi=75)
    plt.close(fig)


nrow = 3
ncol = 3
rng = np.random.default_rng(0)
arr = rng.random((30, 2))
df = pd.DataFrame(data=arr, columns=['foo', 'bar'])
for size in [14, 22]:
    plot_title = f"Font size = {size}"
    plot_group(df, nrow, ncol, size, plot_title)