Question

why it is very hot in summer

Answer 1

It is very hot in summer as the sun is just above the equator and the global warming plays a part in it too.
Hope this won't helps you @_@

Answer 2

Hope it helps @@@@@*****
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Because the earth's axis is tilted. It is all about the tilt of the Earth's axis.
Many people believe that the temperature changes... because the Earth is closer to the sun in summer and far apart from the sun in winter.