First day of spring marks warmer days in Bay Area

SAN FRANCISCO - Spring is officially here.

The vernal equinox arrived Sunday at 8:33 a.m. Pacific time, marking the end of winter and the first day of astronomical spring in the Northern Hemisphere. It’s a reminder that we’re heading toward warmer and brighter days.

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Equinoxes happen twice a year: once in March and once in September. Earth's tilted axis causes the seasons, according to NASA.

Throughout the year, different parts of Earth receive the Sun's most direct rays. So, when the North Pole tilts toward the Sun, it's summer in the Northern Hemisphere. And when the South Pole tilts toward the Sun, it's winter in the Northern Hemisphere.

Saturday's rain event wasn't as strong as expected, and now the Bay Area will be hoping for any signs of moisture as spring begins.