Some 46 per cent of retailers said sales volumes rose in the three months to July, while 25 per cent said they fell.
Retailers expect sales to grow even more strongly in August.
CBI survey panel chair Barry Williams said: "As temperatures began to rise, it seems so did sales volumes."
The hardware and DIY sectors have reported sales rises of 20 per cent, though garden centre sales rises slowed to almost a halt in June and July. But garden centres are still 10-15 per cent up this year.
Meanwhile, Homebase has reported 83 per cent year-on-year increases in sales of slug deterrents. Garden buyer Heidi Towse said copper tape sales were up 400 per cent.