Best times for Dua(supplication): During The Rain:

Narrated Sahel Ibn Sa'ad (RA): that the Messenger of Allah (SAW) said: 'Two will not be rejected, Supplication when the Adhan (call of prayer) is being called, and at the time of the rain'.

[Ref: Al-Hakim 2: 114, and Abu Dawud #2540, ibn Majah]

'Seek the response to your du'as when the armies meet, and the prayer is called, and when rain falls'

[Ref: Reported by Imam al-Shafi' in al-Umm, al-Sahihah #1469].

The time of the rain is a time of mercy from Allah (SWT) so, one should take advantage of this time when Allah (SWT) is having mercy on His slaves.

Mashallah