The light in the shed

There's this rectangular shed in the backyard that I go into fairly regularly. The shed's concrete floor has a long crack in the middle running length-wise, and the gap grows every year due to the shed being built on uneven ground. For now, the shed is still perfectly usable as storage because the crack is mostly hidden underneath some shelving.

The roof is in good shape. Every year during cherry season, I use the roof as an elevated platform to pick cherries from the tree growing right next to the shed. There's raccoon droppings that I have to circumnavigate when I'm cherry picking, but otherwise it's super convenient. Unfortunately the cherries sucked this year, but that's besides the point.

This shed, you see, has a single tubular fluorescent light to illuminate it. It does a good job - when it works. For some strange, unknown reason, the light only turns on 33% of the time when I flick the switch. The percentage used to be around 50% a few years ago, but it's gone down recently. When it's dark out and I have to use the shed, I now go in expecting it to not turn on and am pleasantly surprised when it does turn on. For the times when it doesn't turn on, a feeble glimmer of light still appears at the extremity of the light bulb, as if to taunt me. I can flick the switch on and off a couple times, and still that faint glimmer will appear - but no real illumination. It's only when I give it a couple days and come back another time to try the light that it will magically turn back on.

I think this phenomenon is weather dependant. May be not the temperature, because the likelihood of it turning on doesn't seem to change from winter to summer in any given year; perhaps the humidity, then? Or barometric pressure? Something affecting the electrical connection, somehow. An electrician would probably have an answer, but for now, I'm content with playing a sort of roulette with the light in the shed.