Toronto is approaching the end of astronomical summer the way it opened a lot of days this year — under a sky that can’t quite make up its mind.A mix of sun, cloud and scattered showers is in store for the city this weekend, with the changeover to fall arriving right on schedule a few days later. After a mild, mostly dry Thursday with a high near 25°C, conditions begin to shift heading into Friday. Skies stay mainly sunny with a high around 22°C, but clouds build in overnight as the next system approaches.From there, the weekend turns unsettled:Saturday: A high of 18°C with a 40 per cent chance of showers during the day, climbing to a 60 per cent chance overnight as the low dips to 13°C.Sunday: Similar story — a high of 19°C paired with a 60 per cent chance of showers, clearing to cloudy periods overnight with a low of 10°C.Related:How a ‘super’ El Niño could impact weather in Canada in the coming monthsNeither day is a washout, but anyone with outdoor weekend plans — patio time, a farmers’ market run, one last round of golf — should keep a rain jacket within reach and expect on-and-off activity rather than a steady soaking.Into next weekThe unsettled pattern lingers into the start of the workweek. Monday looks cooler and drier, with a mix of sun and cloud and a high of just 15°C, before temperatures tick back up slightly Tuesday to a seasonal 18°C with a lower, 30 per cent chance of showers. Wednesday brings another round of showers, with a 40 per cent chance and a high near 18°C.Overnight lows through the stretch hover in the 10 to 13°C range — a reminder that summer’s warmth is on its way out, even as daytime highs occasionally flirt with the high teens and low 20s.Say goodbye to summer next weekWhile the weekend forecast will decide whether anyone’s plans get rained on, the bigger seasonal marker lands a few days later. The autumnal equinox — the precise astronomical moment summer ends and fall begins — arrives Tuesday, Sept. 22, at 8:05 p.m. EDT, when the sun crosses directly over the equator and day and night briefly settle into near-equal length across the globe.That makes this the last weekend of astronomical summer, even if Toronto’s weather has already been giving a preview of fall for days. From Tuesday evening onward, the Northern Hemisphere officially tips toward shorter days and longer nights, kicking off a slide toward the winter solstice in December.Click here to sign up for the CityNews Weather Guarantee, with the jackpot sitting at $7,300 as of Thursday.