A duty that never switches off
Section 2(1) is unqualified by any calendar: "Every landlord of a rented or leased dwelling unit shall provide and maintain adequate and suitable heat in all areas of the dwelling unit." The definition section fixes that at "air temperature in the dwelling unit of at least 20 degrees Celsius (20°C)".
Most municipalities that regulate heat attach a season to it. Mississauga does not, which means a cold snap in late June or early September carries the same obligation as one in January.
Section 2(2) provides the two ways out. The duty does not apply where the landlord and tenant "have expressly agreed that the rented or leased dwelling unit will not be heated by or at the expense of the landlord", or where the tenant can directly regulate the temperature such that adequate heat can be maintained — and where that regulation "has been enabled, if necessary, by the landlord". A thermostat the tenant cannot actually reach does not qualify.
Section 3 forbids equipping a rented unit with portable heating equipment as the primary source of heat, which closes the usual workaround for a failing system.
The cooling duty, and its limit
Section 4(1) mirrors the heat duty: every landlord "shall provide and maintain adequate and suitable cooling in all areas of the dwelling unit", defined as an air temperature that "does not exceed 26 degrees Celsius (26°C)".
Section 4(2)(a) is the limit that matters. The duty does not apply where the unit "is not equipped or furnished with an air conditioning system or unit". Mississauga is not requiring anyone to install cooling; it is requiring that cooling which exists actually works.
The same two carve-outs as heat follow: an express agreement that the unit will not be air conditioned at the landlord's expense, and a tenant who can directly regulate the temperature.
Like the heat duty, the cooling duty carries no dates.
Where the thermometer goes
Section 5 fixes the measurement for both duties: "the temperature shall be measured at 1.5 meters above floor level and 1 meter from exterior walls in all rooms intended for normal use by tenants."
That last phrase matters as much as the numbers. It is every room a tenant normally uses, not a single representative reading in the warmest part of the unit.
Mississauga's property standards bylaw, 0654-1998, is a separate instrument and contains no temperature requirement whatsoever — a landlord who checks only that document will conclude the city has no heat standard. It does set a hot water floor of 43 degrees at the tap after thirty seconds of running.