An infantry soldier in the Rifles regiment died on Tuesday while on a training exercise in the Brecon Beacons mountains area of Wales.
Joshua Hoole, 26, died three years after three other soldiers died in the same area.
His grandfather told the BBC he was a “beautiful grandson” and a “super fit boy.”
The Ministry of Defence confirmed the death, which happened on the hottest day of the year so far in the UK The Met Office said the temperature rose to 33.5C in Oxfordshire on Tuesday.
The soldier was from ITC Catterick barracks died on Tuesday while conducting pre-course training for the Platoon Sergeants’ Battle Course.
The Sun reports that the soldier was a senior non-commissioned officer.
An army spokesman told the Sun Online: “We can confirm that a soldier from Infantry Training Centre Catterick died on 19 July while conducting pre-course training for the Platoon Sergeants’ Battle Course in Brecon.”
The news comes after soldiers died in an SAS training exercise in the Brecon Beacons in 2013, also on one of the hottest days of the year.
The SAS hopefuls; Craig Roberts, Edward Maher and Corporal James Dunsby died during “searing heat” in the drill in 2013.
As a result the Ministry of Defence was given a crown censure, the maximum sanction possible - meaning it failed to meet the standards for health and safety set out in law.
The MoD has since promised to put measures in place to prevent further tragedies.