The pattern of seasonal temperature odds across Western Australia is mostly a result of
continued warmth in the central to southeastern Indian Ocean, especially off
the west coast of WA.
Averaged over September to November, the chances of above-normal maximum
temperatures are between 60% and 70% over much of the Kimberley, whilst in
most of western WA there is a 60% to 65% chance of higher than normal maxima (see map).
So for every ten years with ocean patterns like the current, about six or seven
springs are expected to be warmer than average over northern and western WA,
with only three to four cooler. Across the remainder of the state, the
chances of a warmer than average spring for maximum temperature is between 50% and
60%, meaning roughly equal chances for warmer or cooler than normal conditions.
Outlook confidence is related to how consistently the Pacific and Indian
Oceans affect Australian temperatures. During spring, history shows this effect on
maximum temperatures to be moderately consistent across much of eastern WA,
whilst it is only weakly consistent for the remainder of the state
(see background information).
Average spring minimum temperatures are more strongly favoured to be warmer than normal
across WA (see map). The chances of increased overnight warmth (averaged over the
coming three months) are generally between 60% and 80%. So for every ten years with
ocean patterns like the current, about six to eight springs are expected to be warmer
than average across the state in terms of overnight temperatures, while about two to
four are expected to be cooler.
History shows the oceans' effect on minimum temperatures during spring to be
moderately to highly consistent across WA.