Now is the best time of year to get your chimney swept. If you have an open fire, sweeping means you avoid a soot-fall into the hearth when the late summer thunderstorms tip the balance and drop the soot that has been absorbing moisture all summer down your cool chimney. Also, you'll avoid those very unpleasant sooty / tarry smells that happen when it's warmer outside then inside and your chimney starts to draw down into your property rather than up and out.
If you have a wood burning or multi-fuel stove with a stainless steel liner now is the time to get swept to avoid the acidic soot corroding your liner for several months - this year and every year if you don't have an end of season sweep. Liners are usually guaranteed for 10 years (subject to twice yearly sweeping). Get yours done now to prolong it's lifespan. Stainless steel liners are a temporary engineering solution, not permanent. Hence the 10 year warranty. However, if you get them swept now you'll extend their useful life as long as you burn the correct fuel. Also you avoid soot falls onto your stove baffle plate that a) will corrode it b) will smoke if you re-light next season without having had it swept. #StaySafeGetSwept