The Cobblers suffered a third successive home defeat as the gloom descended on Sixfields in more ways than one.
Chesterfield ran out 3-1 winners on a surface which, thanks to a first-half thunderstorm, resembled a ploughed field by full-time.
But the pitch is the least of Northampton’s worries at the moment.
This defeat, which came when the Spireites poured in three goals to wipe out Darren Carter’s early penalty, leaves them six points adrift at the foot of Sky Bet League Two.
They remain without a permanent manager, too, and although the boos were muted at full-time on Saturday, there will now be grave concerns about the team’s future.
Chesterfield had made a bright start to the game but things got gloomy for them just as the weather did.
A corner on the left-hand side was cleared but put back into the box where it fell to Hallam Hope inside the six-yard box.
As he attempted to control it he was brought to ground by a clumsy attempt to get the ball by visiting keeper Tommy Lee.
Referee Graham Horwood pointed to the spot immediately and Carter drilled the spot-kick home with total confidence.
The Spireites got themselves back in the game with a quick piece of thinking that caught the Cobblers completely cold.
A swiftly-taken free-kick put Gardner in down the inside-right channel and he drilled a high shot inside Matt Duke’s inside post before any defender could cover.
Not much football was played between the goals, with players struggling to find their feet in the difficult conditions.
The Spireites’ second goal came through a catalogue of errors.
First, Matty Blair failed to meet a long ball over the top that bounced in open play and then Sean McGinty fluffed his clearance on the edge of the box.
That presented the ball to Eoin Doyle, who slipped a regulation square pass to Gary Roberts.
Roberts should have gone clean through on goal with the ball but it looked as though the large puddle in which the ball stopped would save Town.
James Hurst covered to block Roberts’ first shot but he reacted quickly and chipped the rebound over Duke, who was off his line, and into the net.
Town’s best chance to get back into the game came via a scramble in the six-yard box that was eventually cleared by Ritchie Humphreys from almost on his own goal line.
With the home side attacking, there were great swathes of space behind them and it was into one of these areas that the third goal came.
A clipped pass over the top held up in the mud, McGinty and Duke hesitated and Armand Gnanduillet raced onto it to slot comfortably past the keeper.
Cobblers: Duke, Hurst, Collins, McGinty, Widdowson, Deegan, Carter, Tozer, Blair, German, Hope
Subs: Morris (for Hurst 64), O’Donovan (for Carter 66), Hooper (for Deegan 76)
Not used: Snedker, Harriott, Doumbe, Demontagnac
Chesterfield: Lee; Darikwa, Evatt, Cooper, Humphreys; Ryan, Morsy; Gardner, Banks, Roberts; Doyle
Subs: Gnanduillet (for Banks 62), O’Shea (for Gardner 76), Hird (for Doyle 83)
Not used: Smith, Togwell, Brown, Dunbavin
Away fans: 933