A warm spot or hot spot on the floor is one of the slab leak signs that homeowners often notice first. Hot spots are more quickly and easily noticed on tile flooring where there is a thermally conductive path from the soil under the slab to the surface of the flooring.
If you notice a warm spot on the floor that seems to persist both day and night, do not ignore this! Feel carefully around on the floor with your hands to see if the warmth is concentrated in a particular area. If the spot stays the same or gets worse, this is almost definitely a slab leak.
If you have one, use an infrared thermometer to pinpoint exactly where the tile is the hottest. It can be helpful to put little pieces of masking tape at the spots where you take a temperature measurement and write the temperatures on the tape. This will allow you to see if it changes at all over a couple of days.