Parent Kingfisher cited a "tale of two quarters", with sales of outdoor goods at B&Q falling 11% in February to April, but bouncing back 17% between May and early August.
Volatile weather resulted in a 1.6% dip in adjusted pre-tax profits to £365 million for the 26 weeks to the start of August, but Kingfisher's sales grew 4.3% to £5.7 billion on continued expansion and flattering currency swings.
Kingfisher, which also owns trade counter chain Screwfix and Castorama and Brico Depot in France, said consumers remain nervous about spending across its major markets, despite increasing signs of economic optimism.
July's heatwave compared with a sodden summer in 2012, and saw sales of barbecues leap 26% and charcoal soar 48% in the second quarter. Watering equipment surged 69% and sales of outdoor plant pots rose by a third.
But sales of indoor paint dropped 10% during the quarter as households stayed outdoors. B&Q's DIY sales fell 1% during the half, compared with a market which advanced 2%.
The company said: "It was a tale of two quarters with the coldest weather for 50 years in March and a heatwave in July."
B&Q is "rightsizing" by hiving off surplus space in its stores to companies such as supermarkets. It said plans to shrink its footprint at 18 stores would mean 5% less space, annual rent savings of £16 million and rate cuts of £7 million.
But Kingfisher is expanding its Screwfix business, which saw underlying sales increase 3.6% and total sales soar 14.6% to £313 million, defying a tough market for small tradesmen.
It has launched a Screwfix pilot in Germany, with four outlets due to open next summer, and the brand's website has been rolled out to more than 20 European countries.
Chief executive Ian Cheshire said: "Underlying consumer confidence remains weak in our major markets, so we continue to focus hard on our self-help initiatives to drive growth, margin and cost efficiencies."
Kingfisher's sales in the UK and Ireland dipped 1% on a like-for-like basis, but total revenues edged up 0.3% to £2.3 billion. Profits in the UK and Ireland were broadly flat at £141 million.
Kingfisher has more than 650 B&Q and Screwfix stores in the UK and Ireland, employing more than 25,600 staff.
Europe's biggest home improvement retailer opened a net 29 new stores across Europe during the half, of which 18 in the UK were mainly Screwfix outlets. It plans another 47 new outlets in its second half, including 42 in the UK - again mainly Screwfix branches.