The Tigers looked certain to grab an 89th-minute when substitute Jay Simpson's effort headed for goal, but it was pushed out by Hamer to Sone Aluko six yards out.
But with the goal at his mercy, Aluko was denied by an excellent reaction stop from Hamer to preserve their unbeaten Championship record and guarantee a point.
Powell said: "I suppose it was a fair result on reflection of how the day panned out.
"It wasn't easy and you can't play the football that maybe you'd liked to in these conditions.
"I have to take the positives with regards to it is three games unbeaten.
"I feel we had a very good period in the first half when we put them under a lot of pressure.
"In the second half as it went on Hull got into the ascendancy and Ben Hamer made some good saves.
"Ben Hamer has arguably been our best player in our opening three games.
"Today in difficult conditions, his positioning and his bravery, especially with the double save in the second half, has earned us the point today."
Powell also questioned the assistant referee's decision to raise his flag early in the second half for Bradley Wright-Phillips being in an offside position before strike partner Yann Kermorgant fired into the net.
"Well, that's a goal," he said.
"Bradley Wright-Phillips outstripped their defence and was onside.
"He drew a decent save from Ben Amos and then it was a terrific finish from Yann.
"It's onside and it is a goal."
Hull assistant manager Steve Agnew revealed the game could have been abandoned after a second half downpour but felt the conditions actually brought the best out of the Tigers.
Agnew explained: "It was entertaining, the thunder and lightning brought the game to life.
"It was a game where we thought we had more of the chances and probably could've nicked it.
"We got a whisper that if the rain continued to be persistent and heavy then he might have brought the players off for 10 minutes.
"I thought we had the better of it with shots on target and their keeper made two or three terrific saves.
"Added to that I felt we got into some really good positions and didn't test the keeper as well as we should've done.
"We feel disappointed to go away having not taken the three points.
"They'll be a tough nut to crack at home Charlton, they are good side, they have a lot of momentum and are very strong.
"A point away at Charlton is a good point, they are good on set pieces and have terrific delivery."