In Massachusetts the berries withstand 95-degree temperatures. I can't explain why that is so. The use of tensiometers by Julie and Dave not only drastically cut the costs of water but led to that bumper crop the first year. But numerous customers, growing everything from trees to flowers, report substantial savings in water use and better yields with use of tensiometers. Low numbers mean there is too much water, potentially damaging to the roots.
High numbers mean the roots are starved for water, leading to wilting and death.
The tensiometers are left in place, permitting a daily, even hourly gauge of whether water is needed and how much. In their lifetime Julie and Dave have witnessed the growing popularity of cranberries, particularly juice, in everything from highballs to candy. The result has been a surplus of berries and a collapse in prices. That is only predictable.