I think you get the basic idea—a "sign from God" (to use the words employed by our respective Patriarchs, and to refrain from the word "miracle" so as not to be distracted by semantics), need not be beyond natural explanation. That God can, and that He has/does defy the laws of nature, does not mean that He necessarily must/will, to communicate a message to His creation.
Allow me to share a personal anecdote which is very dear to me, in the hope it may encourage others. I am going through a very difficult time in my life at the moment, having lost a loved one (not to death, though) a few months ago. About a month ago during a break between classes I decided to sit and have lunch at a nearby park. I was in a terrible mood that day; I felt like I had very little to look forward to in life. Nevertheless, I was also quite starving so I was at least looking forward to enjoying a tasty lunch in a nice and peaceful setting.
When I got to the park, all the benches were occupied, and the moment a bench became vacant a second didn't pass before someone laid claim to it. However, I noticed one particular bench which everyone surprisingly seemed to walk past and I managed to get to it just in time. My spirit slightly lifted as I felt I could finally sit down in the warm sun and enjoy some delicious vegetarian thai stir-fry… until I noticed the stench of the fertiliser that was sitting right behind my bench.
I can’t tell you how ticked off I was. I couldn’t be bothered getting up in order to search for another spot, so I just put my lunch away—my appetite being lost—and took out my pocket Bible so as to keep my mind distracted from negative thoughts. I randomly opened the Bible to the section in the Gospel where the Lord Christ commands us not to worry about our life and to seek first the Kingdom of God. In establishing His point, He referred to completely natural phenomena as evidence of God’s caring providence—the birds of the heaven which always manage to find sustenance and the lilies of the field which neither toil nor spin and which yet manage to grow arrayed greater than Solomon in all his glory.
I then noticed some movement in front of me so I put down my Bible to see what was happening. Before me was a gardener; he looked at me cheerfully and said, "Hi mate, sorry about the fertiliser and the disturbance." "That's quite alright," I responded. I looked to my right, and lo and behold, they were none other than lilies that were being prepared to be planted before me. I then looked to my left, and noticed a young mother giving her child small crumbs of bread to throw to the seagulls. The Gospel reading was brought to life for me in a way that seized my conviction in its message in a more intimate and personal way than ever before. I cannot consider the events of that day any less than a "sign of God".