Overall, it is looking one-or-two degrees cooler than the last three Tours and very similar to four years ago, fairly comfortable for competitors and spectators.
As in the 2009 Tour there will be just two days with temperatures in the 30s, only one of those above 35 degrees.
Also as in 2009, Adelaide's average maximum temperature will be about 29 degrees but in the Hills, where most stages will be run, it will be two-or-three degrees cooler.
Stages three, four and five will be the most interesting weather-wise.
Hottest Stage - Stage 3 - starting in about 33-degree heat in Unley and finishing in 33-degree heat in Stirling, at times reaching about 35 degrees.
Coolest Stage - Stage 5 - starting in 20 degrees in McLaren Vale and finishing in 22 degrees at Old Willunga Hill, at times possibly reaching 25 degrees.
In general, the heat won't be as much of a problem as in the last three years but as usual, the wind will be testing, averaging 15-to-30km/h on most days.
Windiest Stage - Stage 4 (Modbury to Tanunda) - southwesterlies reaching 25-to-40km/h with gusts to about 50 km/h.
On the morning of Stage 4 on Friday is the Tour Challenge, an open event, which travels the same course through the Adelaide Hills to Tanunda. The gusty southwesterly winds will generally be a tail-to-cross wind and feel fairly chilly first thing in the morning. It should also be one of the coolest mornings, about 14 degrees at sunrise and only warming to 20 degrees just after midday. The road may be a bit wet but any light showers will have cleared by about sunrise.
Showers are more likely the previous afternoon and evening, possibly affecting Stage 3. It's unlikely to be much, a couple millimetres at most, but it may bring a bit of cooling relief. The road should be dry for all other stages.
Wettest Stage - Stage 3 - brief showers possible, nothing more than about two millimetres if anything at all.
The cool weather is partly due to a slow-moving high south of the state and the onset of the monsoon in the tropics. The high is directing southerly winds over the Adelaide area and the monsoon is helping reduce the heat over central Australia. On the one day when winds turn northerly there will only be moderate heat reaching Adelaide, unlike the heat in the last few years and nothing like 2006.
In the 2006 Tour Down Under the average maximum temperature was about 40 degrees with four days exceeding 40 degrees.
© Weatherzone 2013
12:54 EST Southern New South Wales and the ACT had a chilly start to the weekend, with some places seeing their coldest May night in half a decade.