I'm assuming your resting heart rate is lower than 116?
When you hit 158 or 116, are you feeling any chest pain, shortness of breath, dizziness or any other symptoms? How fast are you walking?
Here's a good article about exercise, target heart rates, etc. - https://www.heart.org/en/healthy-living/fitness/fitness-basics/target-heart-rates Please note these are generalized, and may not apply to you, as it can differ from person to person, depending on age, weight, health status, medications, etc. You should check with your doctor.
Generally speaking, yours is not in the danger zone, provided you aren't experiencing any alarming symptoms. Since it's new for you to reach this level, though, it wouldn't hurt to get checked by your doctor, especially if your route hasn't changed and you didn't have this issue on these same hills before.