Variable won't change when client receives event?

I have the server firing all clients every second to change the value of a TextLabel on screen, and the intermissionTime variable changing every time the client is fired, but for some reason, the intermissionTime variable only changes once, to 29. My code is below. Thanks!

local timer = script.Parent
local intermissionTimer = game.ReplicatedStorage.Events.ChangeTimeIntermission

local intermissionTime = 30

intermissionTimer.OnClientEvent:Connect(function()

    local intermissionTime = intermissionTime - 1
    timer.Text = intermissionTime
    print("client: received server fired, time left is "..intermissionTime)

end)