Tropical and sub-tropical climate
The Mitchell Grasslands is the only landlocked region of the
tropical savannas. They stretch along the southern boundary of the
Gulf region and have a similar elongated shape running in a north
west-south east direction from the Northern Territory to central
Queensland. Most of this area lies in a tropical climatic zone but
southern sections extend into the sub-tropics where more arid
conditions prevail in the characteristic wet summer and dry winter
seasons.
Trade winds
This region's climate is controlled by the south-east trade
winds which persist throughout the year except during the summer
months when the north-west monsoons intrude into the northern
sectors. In summer quasi-monsoons (modified trade winds) bring
warm, moist, easterly to north-easterly winds to the south-east
areas.
Rainfall
More than 80 per cent of rain falls between December and March -
much of which is deposited by thunderstorms accompanying the
monsoons or during the unstable, seasonal transition periods. They
may occur on an average of 20 to 40 thunder days per year, which
are most frequent in the north-west. The climatic effects of
tropical cyclones rarely extend into this region.
Annual rainfall averages diminish from 600 mm in the north to
less than 400 mm in the south making the Mitchell Grasslands the
driest tropical savanna region. Variability of this rainfall is
moderate to high with a high possibility of droughts occurring in
the south. Run-off from heavy summer storms can cause dramatic
changes in river levels over a short period of time.
Average temperature
The region's hottest temperatures occur pre-wet season but the
slightly cooler, maximum January temperatures range between
36ºC and 39ºC when cloud cover and rain are most
frequent. Climate discomfort occurs on 100 to 200 days each year
with the more humid north being most strongly affected. January's
relative humidity levels are around 30-60 per cent which begin to
increase from about October after winter averages of 20-50 per
cent.
Winter
During the longer winter season the south-east trade winds,
which lose moisture as they cross the continent, blow consistently
across the region so conditions are dry, skies are clear and
temperatures are milder. July minimum temperatures range between
9ºC and 12ºC and frosts are a possibility in the far
south-east sector on clear nights.
