Answer
(Fatwa: 1239/1239=M/1430)
(1) It is allowable, but one should not make it habit. If such situation arises one can perform salah at home or a place outside mosque. However, it is better to wait for the jama?ah if there is no so much hurry:
وفي الشامي: یکرہ تکرار الجماعۃ في مسجد محلۃ بأذان وإقامۃ إلا إذا صلی بھما فیہ أولا غیر أھلہ أو أھلہ لکن بمخافتۃ الأذان الخ
(2) If a traveller is in comfort not in hurry, it is better to perform all sunnah salah with fardh. But, if he is not comfortable and is in hurry, he can leave the sunnah salah.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband