merciless heat/cold/wind etcheat, cold etc that is very great or strong and unpleasant, and does not stop 酷热/严寒/凛冽的风等 It brings some relief from the merciless summer heat. 它给夏天的酷热带来些许凉意。
merciless heat/cold/wind etc• During the merciless heat of noon one of the frailer females collapsed, far from any possible shelter.
→ merciless heat/cold/wind etc at merciless(1)