Answer
Wa `alaykum as-Salamu wa Rahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
As for your question, you can skip fasting and make up for it later as long as you are unable to complete it or fear dehydration.
In his response to your question, Sheikh Ahmad Kutty, a senior lecturer and an Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states:
If you are working at a hard job and you are not able to function due to dehydration because of the prolonged hours of fasting, you are allowed to skip the fast, and make up during winter when the day hours are shorter.
Eminent scholars have ruled that people doing manual jobs or working in extreme conditions and they face the risk of dehydration, they may skip fasting and make up for it later.
Allah Almighty knows best.