Unseasonable warmth will push into Adelaide this week before a gusty cool change on the weekend. This Friday Adelaide is likely to have its warmest May day in eight years. In May 2005 it reached 29.2 degrees, the second hottest May day in the last 90 years. The May record of 32.3 degree was set in 1921. The mercury is likely to increase from Tuesday as a warm air mass moves over the region from the interior. On Tuesday and Wednesday it will warm to the mid 20's, well above the average May maximum temperature of 19 degrees. By Thursday, it should reach 27 degrees and become even warmer on Friday as a cold front and trough approach from the west. As the front and trough cross the state over the weekend, temperatures are likely to drop significantly, with only a top of 18 degrees expected on Sunday. Rain is likely to accompany the change throughout the weekend, with potential for some decent falls, more than 15mm.