Can Workers Break the Fast in Extreme Heat?

It is permissible for civil defense workers to break their fast in extreme heat in order to rescue the injured, but it is preferable not to break the fast, except in cases of necessity , and they should make up that day. 

So long as a person is able to complete his fast, it is not permissible for him to break it. But if an accident happens far away, for example, and the sun is burning down in the summertime, and you go there to rescue the injured or put out a fire, and you feel thirsty and are afraid that your thirst will affect you adversely, then in sha Allah it is OK to break your fast. Allah says (interpretation of the meaning):

“So keep your duty to Allah and fear Him as much as you can.” [al-Taghabun 64:16]

“Allah burdens not a person beyond his scope.” [al-Baqarah 2:286]

The Prophet (peace and blessings of Allah be upon him) said:

“If I command you to do a thing, do as much of it as you can.” (Narrated by Muslim, no. 1337; al-Nasai, 5/110)

This applies so long as no travel is involved; if the matter involves travelling , then it is unconditionally permitted to break the fast. 

And Allah knows best.