The group - which has 1,912 shops across the UK - said like-for-like sales lifted 3.2 per cent across its own-managed shops during the 13 weeks to September 29, while total sales rose 7.3 per cent.
This marks a pick-up since its first half, when sales edged 1.5 per cent higher.
But the group said profit margins were hit at the start of the summer quarter by the volatile sales patterns, although this was offset by improved trading since the start of September.
Greggs said: “We were pleased with our trading performance during a period that included a long spell of hot weather, which made sales patterns more difficult to predict.”
The third-quarter performance means comparable store sales are now 2.1 per cent higher in the year to date, with total sales up 5.9 per cent.
Greggs said it remains on track for full-year forecasts, with new autumn ranges including a Pumpkin Spice Latte and Chilli Beef Bake.
It has opened 93 new stores in its financial year so far, including 35 franchised outlets largely at transport locations, while closing 35 shops.
The group plans to open 100 net new stores over the year, having recently pegged back its expectations from a previous target for 130 new shops.