Why does the same temperature feel hotter at night? For example, 70 degrees literally feels hot at night when outside but during the day 70 degrees feels just mild when outside. Why is that? And another example is that it feels hotter at night in your house during the summer than during the day and why is that when it is hotter outside during the day and cooler at night but the opposite when inside your house?
During the day, the sunlight is kept out of your house by the roof (assuming you don't have a glass ceiling or windows on your roof). At night, the sun sets and the outside atmosphere is allowed to emit infrared radiation. If there are clouds out, they emit infrared radiation back down to the surface. The atmosphere, itself, also emits radiation back (greenhouse effect), so the surface doesn't get too cold.
Now let's compare what happens at night in your house. Presumably, your roof and house absorbs a lot of radiation during the day. During the night, your house emits radiation, but more than outside, since it is hotter (Stefan-Boltzmann equation). Your roof/ceiling emits radiation both inside and outside the house. This keeps the radiation "trapped" inside the house.