krits:
T21/2721Z T03/2715Z
This does indeed mean that the maximum expected temperature at this airfield is likely to be 21 degrees and is estimated to happen at 2100Z on the 27th.
Likewise the minimum temperature is expected to be 03 degrees at 1500Z on the 27th.
This is useful information for projected take-off performance purposes. (The higher the temperature - the lower the possible take-off weight from a given runway).
In the old days, aircraft like the Tu104 couldn't even get airborne from airfields such as Bahrain in the summer until the temperature went down after dark!