Extreme heat has forced organisers to shorten today's stage of the Santos Tour Down Under in South Australia. Temperatures are forecast to reach the low to mid forties across a much of South Australia today, which is 10-15 degrees above average for this time of year in many places. The mercury is expected to reach 41 degrees in Adelaide this afternoon, which is 12 above the long-term average. The same forecast tomorrow puts the city on track to register three days over 40 degrees for the first time during January in four years. If Coonawarra reaches its forecast top of 41 degrees this afternoon it will be their hottest day for any month since 2015. While South Australia's State Emergency Service advises the public to limit outdoor activities during hot weather, professional cyclists competing in the Santos Tour Down Under will still be racing. However, the heat-plagued route for Stage 3 from Glenelg to Victor Harbor today has been reduced by 26 kilometres. A public ride that was scheduled to take in Victor Harbor has also been cancelled due to the hot weather. The heat will also help to elevate fire danger ratings to severe or extreme levels today, prompting the Country Fire Service to issue total fire bans in nine out of the state's 15 districts. This includes the Mount Lofty Ranges district, where much of today's racing will occur.