What started as a designated toking time (4:20 p.m.) among high school friends in San Rafael in the 1970s has bloomed into an all-day counterculture weed event. Today, 420, the annual April 20 cannabis celebration, seems about as mainstream as that other intoxicating green holiday, St. Patrick’s Day. A costume ball; science; and food, wine and beer come into play at the greater Bay Area’s cannabis parties.

After Dark Cannabis: San Francisco’s Exploratorium explores the social, judicial, economic and environmental impacts of cannabis legalization. There will be no consumption (just cocktails) at this cannabis-themed edition of the weekly After Dark adults-only gathering, but you can indulge your curiosity about cannabis cultivars through plant displays and demonstrations. The evening also features the Exploratorium’s 650 interactive exhibits exploring perception, art and science. 6 p.m. Thursday, April 18. Exploratorium, Pier 15, the Embarcadero, San Francisco. $14.95-$19.95. Ages 18 and up.www.exploratorium.edu, (415) 528-4444.

420 Spring Blossom Soiree: Attendees are encouraged to dress in costumes inspired by cannabis flowers when San Francisco’s newly remodeled Hotel Kabuki hosts an evening promising cannabis, live entertainment and “a heavenly tea ceremony.” Cannabis will be served and consumed in the private Zen garden — just be sure to preorder cannabis from the event’s state-licensed delivery service and pay in cash separate from your soiree ticket at the door. 8 p.m.-1 a.m. Saturday, April 20.  Hotel Kabuki 1625 Post St., San Francisco. $35-$59 (plus cost of cannabis). Ages 21 and up. http://www.eventhi.io/event/420-spring-blossom-soiree-1242, (415) 922-3200.

Magnolia Oakland 420: Oakland’s only cannabis store, vape lounge and dab bar will host entertainment, vendor-information tables and food trucks. 9 a.m.-9 p.m. Saturday, April 20. 161 Adeline St., Oakland. Free (plus the cost of cannabis and food). $10 store credit for first 100 people. Ages 21 and up. http://www.magnoliaoakland.org,  (510) 628-2119.

Trippy Hill With Berner and Friends: San Francisco cannabis and rap music mogul Berner moves his annual 420 show from the Bill Graham Civic Auditorium to the Midway, the new creative complex in the city’s renewed Dogpatch waterfront neighborhood. The all-day show featuring Berner, Vallejo’s Nef the Pharaoh, Los Rakas and Kool John is a nonconsumption event. 3-10 p.m. Saturday, April 20. The Midway, 900 Marin St., San Francisco. $30. Ages 18 and up. https://www.eventbrite.com/e/420-trippie-hill-featuring-berner-more-tickets-58040064395, (415) 608-2220.

Emerald Pharms 420: The Mendocino County cannabis store and lounge hosts musicians, circus acts, magicians, glass blowers, food trucks and vendors. Consumption and camping will be allowed. Noon-10 p.m. Saturday, April 20. Emerald Pharms, 13771 S. Highway 101, Hopland. Free (plus cost of cannabis, food and $25 camping and $35 RV sites, including showers and bathrooms, at adjacent Solar Living Institute). Ages 21 and up. http://www.eventhi.io/event/emerald-pharms-420-festival-992, (707) 669-4819.

Hippie Hill 420: Due to timing, San Francisco’s long-running Hippie Hill 420 gathering won’t partake of a new state law and a new local ordinance allowing cannabis sales and consumption at events in venues beyond fairgrounds. Bring your own and enjoy music and cannabis culture bonhomie. 9 a.m.-5 p.m. Saturday, April 20. Golden Gate Park, north entrance near Stanyon and Haight streets. Free. Ages 18 and up. http://www.420hippiehill.com