high season 
noun chiefly British
The most popular time of year at a resort, hotel, or tourist attraction, when prices are highest: a sandy beach with plenty of room—even in high season [as modifier]: the high-season price...
- If you're lucky, you might even find low-season prices combined with high-season weather.
- Until August 31, the Grenadines island of Petit St. Vincent - known for its two miles of white beaches - is offering 35 percent off its high-season rates.
- But the numbers in town can fluctuate significantly, with Noble estimating 4,300 permanent residents and 10,000 people on a holiday or high-season weekend.