The term “climate justice” has been in vogue for the last few years, though not everyone may grasp its meaning. “Cooked: Survival by Zip Code” is a new documentary that makes that meaning painfully clear.

The film, which is screening in the San Francisco Jewish Film Festival, tells the story of the 1995 summer heat wave that killed 739 people in Chicago, almost all of them in the city’s poorest neighborhoods. For the July 22 showing at the Castro Theatre in San Francisco, Judith Helfand, the film’s director and producer, will be on hand to accept the festival’s 2019 Freedom of Expression Award and engage in conversation with Nico Opper, a professor of film at Santa Clara University.

The notion of climate justice underlies the film’s focus, opening with scenes of flooding from Superstorm Sandy in 2012 (which Helfand rode out with her mother in Westchester, New York) and New Orleans’ inundation from Hurricane Katrina in 2005. The latter, with its heavy toll on the city’s predominantly African American Ninth Ward (a neighborhood that has yet to recover), was foreshadowed a decade earlier by the Chicago heat wave.

Over the course of five days in July 1995, a searing heat that reached a high of 106 degrees killed scores of people, many of them sick and elderly stuck in their homes with no air conditioning and with windows nailed shut to prevent burglaries. As Helfand depicts with news footage, the death toll overwhelmed the city’s coroner; at least nine gigantic refrigerated trucks were brought in to store the bodies.

Meanwhile, in Chicago’s tony Loop district and North Side, the heat wave was little more than a summer’s unpleasantness. Helfand, who appears on screen throughout as reporter and moral compass, concludes that the natural disaster was in truth man-made.

Helfand goes back decades, to the 1940s, when federal housing officials rendered Chicago one of America’s most segregated metropolises, relegating the city’s poor to the south and west sides. Those communities held their own when America’s manufacturing dominance held sway, but over time, crime, drugs, neglect, urban decay and racism took their inevitable toll. Those neighborhoods were sitting ducks for the slow-motion disaster that came in the summer of 1995.

Helfand, who previously tackled environmental toxins in “Blue Vinyl” (2001) and DES, a drug linked to a rare cancer, in “Healthy Baby Girl” (1997), does not shy away from pronouncing judgment on the inequities revealed in “Cooked.” She notes the irony of a first responder’s disaster preparedness drill in case of tornado (Chicago suffers about one tornado death annually) compared no action to halt the city’s estimated 3,200 deaths each year from poverty-related problems.

The film isn’t a wall-to-wall bummer. Helfand tags along with community organizers in Chicago’s African-American neighborhoods (where it’s easier to buy a gun than a tomato) as they launch healthy food trucks and urban vegetable gardens. One scene showing a teen taking a bite out of his very first apple is simultaneously moving, shocking, joyful and deeply sad.

Though there is nothing overtly Jewish in the film, Helfand as both filmmaker and social justice warrior embodies the Jewish value of pikuach nefesh (saving a life) and hashomer anochi (my brother’s keeper). Chicago — and entire world — could use more keepers like Helfand.

“Cooked: Survival by Zip Code,” 5:30 p.m. July 22 at Castro Theatre, S.F.; 3 p.m. July 24 at CinéArts, Palo Alto; 11:45 a.m. Aug. 3 at Piedmont Theatre, Oakland. The director will appear at S.F. and Palo Alto screenings. Not rated, 76 minutes. sfjff.org