Hillary Clinton’s big night — a moment the former first lady and secretary of state has worked decades to achieve — could be a stormy affair, as disgruntled Bernie Sanders supporters threaten to disrupt her acceptance of the Democratic nomination for president, at the same time a vicious storm threatens to hit Philadelphia.

A severe thunderstorm watch was put in place for Philadelphia late Thursday, and the rain already is coming down as convention-goers stream into the Wells Fargo Center.

The convention all week had been blanketed by 90-degree heat and oppressive humidity -- broken when thunder clapped over the convention hall and sent attendees running for cover Thursday afternoon.

The National Weather Service said more than 2 inches of rain could fall, as the six-day heatwave came to an end, Philly.com reported. The watch is in effect until midnight, while a flash flood watch is in effect from 6 p.m.

Meanwhile, Sanders supporters are planning another night of protests. It’s unclear whether more delegates plan to walk out during Clinton’s nomination acceptance speech.

But outside, protesters are planning to brave the weather to make one last convention stand against the party’s nomination. One protester said a group planned to head to the park near the convention hall.

“We have marched in the rain and it won't stop us tonight,” he said.

Meanwhile, anti-Clinton and other demonstrators were holding events Thursday encouraging voters to “de-register” from the party.

They’re operating in part under the Twitter hashtag #DemExit, one that Green Party candidate Jill Stein has deftly been using as she openly appeals to Sanders supporters to join her team outside the Philly convention arena.

“DNC wants your support for lying, undermining, and insulting you. They'll lock you out if you don't comply. #DemExit,” Stein tweeted.

Stein has proven to be a chief agitator, as Bernie Sanders himself rejoins the fold and urges Democrats to get behind Clinton’s campaign. Even the celebrities are split, with liberal Hollywood stalwarts like Susan Sarandon standing with the Sanders crowd this week.

The efforts hang over the final day of a raucous convention, where Sanders supporters from the start have protested how their candidate was treated by the party brass, particularly after leaked DNC emails pointed to a pro-Clinton bias inside headquarters. Chairwoman Debbie Wasserman Schultz resigned in the wake of the leak, but that didn’t stop protests inside and outside the hall.