With a fan oven, the temperature will be the same in any part of the oven. With a gas oven and no fan, the temperature will be hottest at the top. With an electric oven with no fan, it depends on the placing of the heating elements. It's possible for side-mounted elements to radiate heat in such a way that the centre of the oven is the hottest part. In the same way, bottom-mounted elements may radiate to make the bottom hottest. Note that with these radiant heats the air in the oven will still be hottest at the top