The hottest time of day is usually in the afternoon. The exact time depends upon season and location. There is typically a lag between when the sun is highest in the sky, solar noon, and when the temperature is greatest.
When the sun rises, the part of the Earth receiving its light does not warm up immediately. Rising temperatures, or thermal response, at the planet's surface is delayed. For example, though sunrise happens early during summer months, the highest temperature of the day typically occurs during mid-afternoon. Because sunrise is later in the winter, the interval between solar noon and the hottest part of the day is often later in the afternoon.