The unseasonable May heat is set to finally end in South Australia, with cooler temperatures and rain over the weekend. Temperatures have been sizzling across the state throughout May, with another warm day today. On Wednesday, Adelaide had its second hottest May day on record reaching 31.1 degrees. Thursday was also a sizzler with a top of 29.8 degrees and the maximum has hit 29 degrees today. This makes it the warmest three day period in May since 1921. Mount Gambier in the state's southeast had its warmest May day since 1967 yesterday reaching 27.8 degrees, and has already reached 27 degrees today. In the west, it is again reaching into the low 30's, which has happened every day so far this month, including all time May records earlier in the month. The daytime heat stuck around during the night over some parts due to cloud cover. Adelaide saw its second warmest May night on record, dipping to just 21 degrees this morning. Robe only dropped to 18 degrees, its warmest May night since 1937, while Elliston only dropped to 21 degrees, its warmest May night in 49 years of records. Relief is finally on the way as a strong cold front and associated low pressure trough approach from the west. The system will cross the state this weekend and will be accompanied by widespread rain and isolated thunderstorms, with much cooler temperatures in its wake. The rain will start late this evening in the west, and progressively spread east during the weekend. This rain will be welcomed with open arms by many, with large parts of the state seeing barely a drop the whole month. However, for others this will put a dampener on Mother's Day celebrations, with places from Adelaide and east likely to see their wettest day on Sunday. Widespread falls of 5-10mm are likely across the state over the weekend, with potential for as much as 20-40mm over parts of the west and south. The northeast should see the least from the system, with parts of the Northeast Pastoral possibly not even seeing a drop of rain. Rain should clear by the start of the working week as a high moves over the state, although showers should persist along the coast until mid-week. Temperatures should be near-to-below average in the wake of the front, with frosty mornings likely away from the coast due to clear skies.