Hartley clinched the Kent League Premier Division title after receiving 10 points from Saturday’s incomplete game against Sandwich Town at Culvey Close.
Second-placed Sevenoaks Vine, who despite having a game in hand (at Tunbridge Wells on Monday), cannot catch Hartley now.
Sandwich posted 275 all-out before the rain arrived during the tea break.
South African Jacobus Maritz top-scored for second-bottom Sandwich with his highest score in the league, 88 from 61 balls. His innings included nine fours and five sixes.
Tom Chapman (45) and Ashleigh Cox (35 not out) also made valuable contributions while Kent duo Ryan Davis (17) and Callum Haggett (22) also made starts.
Former England and Kent wicketkeeper Geraint Jones was out for four, one of Daniel Redwood’s (3-37) victims.
Sandwich are now only nine points behind the side above them, Bromley, ahead of Saturday’s final round of fixtures.
Sevenoaks Vine were 45-run winners at relegated Folkestone.
Vine batted first and were all-out for 183 with Thomas Jones taking 6-27.
Opener John Bowden (62) and Harry Levy (52) shared a second wicket partnership of 90.
Harry Levy then took 5-21 as Folkestone were dismissed for 138 with James Lilley making 34 and Sam Ireland 33.
In the only other game to beat the weather, Lordswood won by six wickets at Tunbridge Wells after chasing down 236 all-out.
Opener Nick Selman hit 107 for the home side before being dismissed by off-spinner Ranjit Singh.
Singh finished with 7-41 as Tunbridge Wells collapsed from being 178-3 at one stage.
Openers Palash Joshi (62) and Shaun Piesley (24) laid the foundations for the run-chase with a 68-run partnership before Greg Smith (59) and Chris Piesley (45 not out) completed the job.
Beckenham opener Chris Isles scored the first hundred of his season, 106 not out, at Bromley before rain arrived with his side on 296-4.
Will MacVicar scored 75 while big-hitting Kent star Alex Blake smashed six sixes during a 15-ball innings of 44.
Blackheath were dismissed for 161 by visitors Bexley with Warren Lee making 72.
George Wells was unbeaten on 41 as Bexley reached 64-1 when play was abandoned.