No, heavy rain cannot stop lava.
Lava is extremely hot, reaching temperatures of over 1,000 degrees Celsius (1,832 degrees Fahrenheit). Rainwater would simply evaporate upon contact with the lava, turning into steam.
While rain can cause minor cooling effects on the surface of a lava flow, it is not enough to significantly alter the flow's path or stop its movement.
The immense heat of the lava would quickly overcome any cooling effects of the rain.
In fact, the interaction of lava and water can be dangerous, creating explosive steam eruptions that can hurl hot rocks and debris.
