During the last few days the temperature where we live has been going up. During the day it is around 40 degrees Centigrade. Will the tub of powdered formula I have been using for my four month old go bad at that temperature?
I looked at one manufacturer's recommendation for storage of their formula products to get this answer.
For unopened cans of Similac® infant formulas, most desirable storage temperatures are between 13°C [55°F] and 24°C [75°F], but between 0°C [32°F] and 35°C [95°F] is also acceptable. Storage at extreme temperatures compromises the quality of the product. For that reason, you should not use infant formulas stored for long periods at extreme temperatures.
Your brand may be different, but powdered infant formulas all follow the same general recipe. Unless the manufacturer explicitly says so, there is a risk that high temperatures can affect the formula and so you should find somewhere to store it that is at least consistently below 35°C, and preferably below 24°C.
To make things more complicated, however:
Do not store cans of powder infant formula in the refrigerator. Instead, store them covered, in a cool, dry place.
If you can find a cool, dry place (perhaps a kitchen cupboard that doesn't get frequently opened during the day), that is the best solution until the heat wave is over.