Local and regional dust storms often occur on Mars, but only few of them grow in size to become global phenomena that can last for months. This happens only every three to four Mars years, with one Mars year lasting about two Earth years. Although Martian dust storms are very impressive, due to Mars’ lower atmospheric pressure they are generally weaker compared to hurricanes on Earth, with less than half the typical hurricane wind speed.
Dust storms occur statistically more often in the northern autumn and winter season when Mars is around perihelion, which is the closest point to the sun. On its elliptical orbit around the sun Mars receives more sunlight at perihelion, so the atmosphere warms up which causes the air to move.