、、。
If it rains, we'll call off the mountain hike.
Literal
Rainy-weather [conditional-なら], mountain-climbing [topic-は], cancel.
雨天 ('rainy weather') is a formal compound — 雨 'rain' + 天 'weather' — seen on event notices and signage (雨天中止 'cancelled in case of rain'). 取りやめる ('to call off, cancel') is slightly more formal than やめる. The deliberate comma pacing gives this a measured, announcement-like cadence.