Start all the clocks, reconnect the telephone and warn the replica shirt supplier that overtime may be required. Fernando Torres has scored for Chelsea.

Thunder, lightning, a monsoon, and Torres's first goal for Chelsea. A change in the weather, indeed. Treacherous conditions that threatened to ruin the match instead contributed to 90 minutes of almost continuous drama, culminating in a moment that will make the Spanish striker, his team-mates and their supporters believe that their season is not dead. If Torres could score after 13 barren appearances in the blue No9 shirt, anything can happen.

Torres came on to replace Didier Drogba in the 76th minute, and almost everything he did thereafter was impressive. With his first touch he squared the ball neatly for Nicolas Anelka, his fellow substitute, whose shot was blocked on the line by Danny Gabbidon. The next thing the Spaniard did was score, haring into the penalty area on a diagonal path and readjusting quite brilliantly when the ball stuck on the waterlogged pitch, turning back to guide a left-footed shot past Green's right hand. And in the fourth and final minute of stoppage time his pass from the right, misread by Anelka, rolled through to Florent Malouda, whose drive completed the victory.

A couple of minutes before the interval, just as Frank Lampard was receiving the congratulations of his colleagues for giving Chelsea the lead, a second peal of thunder rumbled around the stadium. Some of the floodlights went out, and the rest flickered. Javier Hernández might have struck to give Manchester United a last-ditch victory three hours earlier and 200 miles away, but the fates seemed to be announcing the start of the final act in this most inscrutable of championship races.

For the real turning point we will probably have to wait until a week on Sunday, when Chelsea travel to Old Trafford. In between times the west London side entertain Tottenham Hotspur while United visit Arsenal. The match in Manchester on 8 May is likely to take place on a knife-edge.

Saturday's fixture, staged between two teams experiencing very different kinds of desperation, should not have required the attention of the special effects department. But a torrential downpour provided the overture, and the first crack of thunder marked the end of an inconclusive opening half-hour and the intensifying of the contest.

Once again Torres was left on the bench – for the sixth time in the last seven league matches – with the manager, Carlo Ancelotti, preferring the all-Ivorian partnership of Didier Drogba and Salomon Kalou, the younger of the pair having scored in Chelsea's last two matches, against Birmingham City and West Bromwich Albion.

After several days of baking heat, the rain began to fall a couple of minutes before the kick-off, coming down in big summer droplets and with such density that the players were soon sploshing around with an air of suppressed anxiety, as if uncertain whether a pass was going to stop dead or skid beyond its intended recipient. Kalou should have opened the scoring in the third minute when he failed to beat Green from close range after running on to Drogba's flick, but the thunder came as West Ham were experiencing their best spell of the match and it felt like a reversal of the tide when Ashley Cole turned Drogba's perfectly weighted pass back across the goalmouth into the path of Lampard, who smashed it into the roof of the net.

The half-time entertainment featured an appearance by Bobby Tambling, Chelsea's record scorer, whose 202 goals included a pair registered in the classic 5-5 draw between these two sides at the Bridge in December 1966. The rain had returned with even greater ferocity and poor Tambling's Chelsea umbrella immediately blew inside out, drenching the 69-year-old as he completed his lap of honour.

The thunder rumbled again as Phil Dowd blew his whistle to start the second period, with the pitch so soaked that the construction of coherent moves became almost impossible. But the excitement never stopped building and both sides lived dangerously before Torres lit up the murk with his moment of redemption, promptly disappearing under a mass of delighted team-mates. If he and they can sustain the momentum at home to Tottenham on Saturday, they will go on to meet a Manchester United side who will have played three games – including both legs of their Champions League semi-final against Schalke – to Chelsea's one. The contest, like the £50m striker's career, is alive again.