Some 39% of mothers and fathers of schoolchildren rein in their spending in June to boost their budgets during costly months of July and August, deals website Groupon found, putting aside an average of £220 during this month.
Nearly one in 10 (9%) parents claim they start planning and saving for the summer holidays as far as six months in advance.
Meanwhile, over a third (35%) of parents find themselves having to make cutbacks at the end of the summer holidays after blowing the budget.
Parents typically estimate they spend £251 on activities keeping their child or children occupied while they are off school during the summer.
On top of this, they spend an added £138 more than the usual household outgoings during term time, bringing while their children are off school, parents' total extra spending over the summer break to an estimated £389 per family on average.
Nearly two-thirds (61%) of parents try to plan activities for their children before the summer holidays start but 45% admit they are struggling for new ideas by the end of August.
The average parent estimates they make 13 suggestions to their child every week during the summer break to help keep their child or children entertained and the average child starts to get bored just after 1.30pm on a typical day during the summer break.
This summer could prove a particular squeeze on parents' wallets, with Inflation hitting its highest level in nearly four years in May.
Figures from Office for National Statistics (ONS) last week showed the Consumer Prices Index (CPI) measure of inflation reached 2.9% in May, the highest level since June 2013.
Julie Szudarek, international president of Groupon, which has created a "summer sorted" calendar to help give families ideas for summer activities, said: "Parents are bombarded on a daily basis by images of perfect family scenes, relaxing holidays and calm reading sessions, but we know the reality is usually far more chaotic."
The research included a survey of 2,000 parents from across the UK with children at primary or secondary school and a further survey of 1,000 parents with a child under the age of 18.