Rain is falling at an angle ${30}^{\circ }$ with vertical with velocity 2 m/s. It may appear to fall vertically to a man who is running with a speed.

$\mathrm{sin\theta } =\frac{{\mathrm{v}}_{\mathrm{m}}}{{\mathrm{v}}_{\mathrm{R}}} \Rightarrow \frac{1}{2}=\frac{{\mathrm{v}}_{\mathrm{m}}}{{\mathrm{v}}_{\mathrm{R}}}\Rightarrow {\mathrm{v}}_{\mathrm{m} }= 1\mathrm{m}/\mathrm{s}$

For a man to see only vertical component of the rain man must run horizontally with 1m/s in the direction of horizontal component of rain.