How to increase plt.title font size?

import matplotlib.pyplot as plt
plt.figtext(.5,.9,'Temperature', fontsize=100, ha='center')
plt.figtext(.5,.8,'Humidity',fontsize=30,ha='center')
plt.show()

Probably you want this. You can easily tweak the fontsize of both and adjust there placing by changing the first two figtext positional parameters. ha is for horizontal alignment

Alternatively,

import matplotlib.pyplot as plt

fig = plt.figure() # Creates a new figure
fig.suptitle('Temperature', fontsize=50) # Add the text/suptitle to figure

ax = fig.add_subplot(111) # add a subplot to the new figure, 111 means "1x1 grid, first subplot"
fig.subplots_adjust(top=0.80) # adjust the placing of subplot, adjust top, bottom, left and right spacing  
ax.set_title('Humidity',fontsize= 30) # title of plot

ax.set_xlabel('xlabel',fontsize = 20) #xlabel
ax.set_ylabel('ylabel', fontsize = 20)#ylabel

x = [0,1,2,5,6,7,4,4,7,8]
y = [2,4,6,4,6,7,5,4,5,7]

ax.plot(x,y,'-o') #plotting the data with marker '-o'
ax.axis([0, 10, 0, 10]) #specifying plot axes lengths
plt.show()

Output of alternative code:

PS: if this code give error like ImportError: libtk8.6.so: cannot open shared object file esp. in Arch like systems. In that case, install tk using sudo pacman -S tk or Follow this link

fontsize can be assigned inside dictionary fontdict which provides additional parameters fontweight, verticalalignment , horizontalalignment

The below snippet should work

plt.title('Temperature \n Humidity', fontdict = {'fontsize' : 100})