Question Summary:
When does the time for zuhr prayer end?

Question Detail:

When does the time for zuhr prayer end? May we pray the zuhr after the time of asr has set in but BEFORE the asr prayer? This is not normal circumstances this would be while travelling and could not pray the prayers on time. 

Answer :

In the Name of Allah, the Most Gracious, the Most Merciful.
As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuh.
The Zuhr Salat commences at midday when the sun moves away from the zenith. The time for Zuhr continues until everything is twice its length in addition to the length it was at midday. (Bahishti Zewar; pg. 133; Zam Zam Publishers; Ed 2005)
 
The time for Asr salat commences as soon as the time for Zuhr Salat terminates as mentioned above. Asr time remains until the sun sets. However, it is disliked to perform salat when the colour of the sun changes to pale yellow. (Bahishti Zewar; pg. 134; Zam Zam Publishers; Ed 2005)
 
With regards to your specific question on performing Asr Salaah, you are referring to the concept of Jama Bain al-Salatain (Combining two prayers) in all probability. According to the Hanafi Madhab, it is not permissible to join two Salaats in
one time. Every Salaat must be performed in its prescribed time.
 
Apparent joining of two Salaats is permissible, not real joining. Apparent
joining is to, for example, delay Dhuhr Salaat until before its expiry time
and perform Asr Salaat immediately upon Asr Salaat time setting in. the same
may be applied for Maghrib and Esha Salaats.
 
 
 
And Allah Ta’āla Knows Best
 
Ismail Desai
Darul Iftaa
South Africa
 
Checked and Approved by,
Mufti Ebrahim Desai.