The greek connatation of the word's prayed earnestly is an interesting emphasis it actually says that elijah prayed in prayer like when jesus said to his disciples in luke 22 vs 15. How do you desire something with desire? Or pray in prayer? It's a way of strengthening the communication. Thus by including the word earnest he helps us understand the strenght of what he wanted to communicate. It means heartfelt,continued prayer like the amplified classic version put it (james 5 vs 16). 1kings 17 gives us the details of what transpired during the course of prayers(1kings 17 vs 1). Elijah didnt just say there will be no rain according to my word just because he felt like it no! The 18 chapter let us know elijah did what he did at the word of the lord. When it was time for the drought to end he prayed in praye again or like the king james puts it he prayed earnestly it was heartfelt and continued until he had the desired result (1 kings 17 vs 18 )