Temperatures on Earth are suited for life unlike anywhere else in our Solar System. Venus is the hottest planet in our Solar System reaching temperatures of more than 400°C while Uranus is the coldest planet dropping to temperatures of -224°C. However, Earth’s average temperature is about 14 or 15 degrees Celsius although it varies a few degrees depending on your source. The hottest temperature recorded on Earth was 70.7°C (159°F) in the Lut Desert in Iran; the temperature was recorded by a NASA satellite. The coldest temperature recorded on Earth – which was measured by the Russian Vostok Station – was -89.2°C (-129°F) on July 21, 1983 in Antarctica.
These were only the highest and lowest recorded temperatures on Earth so far. They also are somewhat limited because temperatures have only been recorded for less than two hundred years. Thus, throughout history the recorded highs and lows have probably been beaten. This is especially true because of climate change, which has occurred a number of times through the millennia. An ice age is one example of climate change.
Temperatures also vary by region and season. Temperatures on Earth are colder at the North and South poles than they are at the equator because of the tilt of the Earth’s axis. Seasons and temperature changes do not result from our planet’s distance from the Sun. The change in distance is too little to have that big of an impact. The seasons affect what temperature it is on Earth. In summer in the Northern Hemisphere, the Earth is tilted so the Sun is higher in the sky and strikes that hemisphere more directly, which causes higher temperatures. In winter in the Northern Hemisphere, the Earth is tilted so that the Sun is lower in the sky and less sunlight reaches Earth resulting in lower temperatures. The seasons are switched in the Southern Hemisphere, so while it is winter in the Northern Hemisphere it is summer in the southern one.
Not every region has four seasons though. At the equator, the temperature is on average higher and the region does not experience cold and hot seasons. This is because the amount of sunlight the reaches the equator changes very little, although the temperatures do vary somewhat during the rainy season. The temperature usually ranges from 18°C to 27°C.
The closer one gets to the Earth’s core, the hotter it is. Although scientists have been unable to directly measure the temperature of the Earth’s core, they estimate the inner core reaches 7,000 degrees Celsius. The upper mantle near the Earth’s crust is about 870 degrees Celsius.
Astronomy Cast has an episode on Earth you will want to check out.