First-half goals from Brandao and Pierre-Emerick Aubameyang were followed by a third from Yohan Mollo three minutes after half-time.
Montpellier immediately pulled a goal back through Remy Cabella before the match was delayed for 30 minutes when the snow made conditions unplayable.
With fears the game could be called off the ASSE players helped clear the pitch and their efforts were rewarded after the resumption with a fourth goal, through Mathieu Bodmer, and a sixth successive win in all competitions.
Bordeaux, however, slipped out of the top five after slumping to a 1-0 defeat at improving Ajaccio.
A first-half strike from Ricardo Faty was enough to earn Ajaccio the spoils as Bordeaux suffered only their second defeat in 13 matches in all competitions.
Valentin Eysseric's late equaliser secured Nice a share of the spoils from a 1-1 draw with fellow Europa League hopefuls Lorient at the Stade Municipal du Ray.
Eysseric coolly slotted home eight minutes from time to cancel out Lucas Mareque's 75th-minute opener for the visitors.
The draw lifted Nice to fifth in the standings, with Lorient three points and three positions worse off.
Reims won away from home for the first time since returning to the top flight as Nancy's resurgence was halted with a 2-1 home defeat.
The Lorraine side had won their last two games and took the lead today through defender Sebastien Puygrenier on the half-hour mark.
But goals from Floyd Ayite and Odair Fortes in the second half turned the game around and Gaetan Courtet had a late third disallowed.
Brest remain just two points clear of the relegation zone after losing 2-1 to Valenciennes at the Stade du Hainaut.
First-half goals from Mathieu Dossevi and Rudy Mater were enough to secure a win that leaves VA 10th in the table.
Charlison Benschop hit the post for Brest in the second half but they had only Florian Raspentino's late goal for consolation.
Elsewhere, Troyes moved off bottom spot with a goalless draw against a Sochaux side who also remain in deep trouble in the battle to survive.