How do I tell if my olive needs more water or less?

The growing setup makes a big difference. In a pot with a very gritty mix, especially in strong sun and high heat, the soil can dry quickly, so a fixed once-a-week schedule may leave it thirsty. Water thoroughly, then check how quickly the mix dries and water again when it needs it. Don’t leave the pot sitting in water.

For an olive planted in the ground, frequent heavy watering can be too much if the soil stays wet. Check the soil around the root zone instead of going by the weather alone.

If it’s planted in the ground, I’d be wary of watering every other day without checking the soil first. Give the root area a chance to dry somewhat between deep waterings. Grass growing right up to a young tree can also compete for water, so clearing a wider area around the trunk may help.

Hot weather can stress a tree, but soaking already-wet soil won’t fix that. Look at the soil a few inches down and adjust from there.

A few older leaves dropping can be normal, but widespread yellowing or a sudden increase in leaf loss points to stress. Check whether the soil is staying soggy, drying out very fast, or whether the problem is limited to older leaves. That pattern is more useful than guessing from the yellow color alone.

I’d hold off on more fertilizer until watering and drainage are clearer. If the tree is in an inert gritty mix, it may need some nutrients over time, but use a restrained amount rather than trying to correct the symptoms quickly.