diff --git a/ca_weathers/ambient.lua b/ca_weathers/ambient.lua
index 98522c2..56908cb 100644
--- a/ca_weathers/ambient.lua
+++ b/ca_weathers/ambient.lua
@@ -14,7 +14,9 @@ end
 
 -- maps range of 0 to 1 to any other range
 local function map_range(val, low, high)
-	return (val + low) * (high - low)
+	local cal_val = math.min(math.max(val, 0), 1)
+	local range = high - low
+	return low + (cal_val * range)
 end
 
 local function generate_effects(params)