Rotation of colorbar tick labels in matplotlib
If you're happy with tick locations and labels and only want to rotate them:
cbar.ax.set_xticklabels(cbar.ax.get_xticklabels(), rotation='vertical')
You can use cbar.ax.set_xticklabels to change the rotation (or set_yicklabels if you had a vertical colorbar).
cbar.ax.set_xticklabels(clevs1[::1],rotation=90)
EDIT:
To set the ticks correctly, you can search for where in your clevs1 array the first tick should be using np.argmin, and use that to index clevs1 when you set_xticklabels:
tick_start = np.argmin(abs(clevs1-clevs[0]))cbar.ax.set_xticklabels(clevs1[tick_start:],rotation=90)
This is the idiomatic way to rotate tick labels as of Matplotlib 3.4 (and very likely earlier versions too)
cbar.ax.tick_params(rotation=45)