Sydney is heading for its third hottest day on record on Tuesday with temperatures staying hot well into the evening. Sydney is enjoying relatively comfortable weather today, with the city reaching only slightly above the January average of 26 degrees. Tomorrow is a completely different story with the mercury likely to reach a staggering 17 degrees above average, topping out near 43 degrees. Across Sydney air conditioners will be working hard all day while those who aren't at work will flock to beaches, pools and shopping centres to keep cool. People are advised to drink plenty of water and to beware staying in the sun for long periods. Normally when the temperatures soar in the Sydney region, the city is at least a few degrees cooler than the west. However, tomorrow there will be very little difference as the usual afternoon sea breeze is unlikely to develop. The lack of sea breeze means that it will be a very dry day, making 43 degrees feel closer to 40 degrees. Fire Danger will be rated extreme for the Sydney region, which is the second highest rating. The very hot and dry conditions will also be matched by moderate to fresh winds in the Sydney area. This will bring one of the worst fire danger conditions for Sydney in many years. Very hot conditions will stick around into the night with lingering in the low to mid thirties well into the evening. This will make sleeping very difficult and uncomfortable for most people. Relief will finally come in the form of a cool southerly change around two or three in the morning. Coastal locations will gain the most benefit from the change while western suburbs will only get a gradual cooling into the morning. Many will be happy to hear that Wednesday will be near average across the Sydney Basin, but further heat is coming on Saturday. At this stage the 40 degree temperatures are only likely to happen in western suburbs due the cooling affect of the sea breeze in the east.