New York, Sep 22 (IANS): Tired of hot days and sweaty nights? Well, autumn is here! At 7.59 a.m. Sep 23, autumn will officially begin in India and the rest of the Northern Hemisphere.

This also marks the start of spring in the southern half of the globe, space.com reported.

According to the US National Weather Service (NWS), the autumnal equinox (meaning "equal nights" in Latin) falls on either Sep 23 or 24 because of irregularities in the calendar and the Earth's orbit.

The spring equinox happens in March.

"In both cases, the Earth's axis is not tilted toward or away from the sun," NWS officials were quoted as saying.

The date is called an equinox because both day and night are of equal length across the globe.

During each equinox, the sun is exactly over the equator at noon.

As the Earth turns, the sun's rays are refracted, or bent to make it look like the sun is above the horizon for a longer period of time, even though it is not, NWS officials said in a statement.

Though this happens with every sunset, it's longer during the equinox.

Also, the days last longer at places farther from the equator because the sun takes longer to rise and set, the report added.