I have several gasoline engines at home (snow blower, lawn mowers, 2 riding lawn mowers, 2 generators, log splitter). In cold weather, all of them are a little more work to fire up. My push mower is the best example. In the Summer, one pull and it fires right off! Never misses. In the winter, I may have to pull the starter rope 20 times before it fires (if it fires at all).
Those machines that have a gas turn-off (petcock), I'll turn the gas flow off and then let the engine run dry until it starves itself for fuel. This way, gasoline will not have a chance to gum-up the carburetor.
Also, I have found keeping Sta-Bill in the fuel tanks helps also, starting in cold weather. I have one riding lawn mower, when it gets below a certain temperature, it simply will not power up. The battery will run dead before it fires. I give up on that one in the coldest weather. When the temps warm up above freezing, it will fire up just fine again. It' just the nature of a small gasoline engine.
Basically, what you are experiencing is pretty typical. Bottom line, the colder it gets, the more difficult they start.