The expected on-time share is an estimate from days with similar weather in our own history.

Rain, snow and cold slow buses down. We compare a month with what we would expect from days that had the same kind of weather.

The weather we use

Daily figures for Ottawa Macdonald-Cartier airport from Environment and Climate Change Canada: highest temperature, rain, snow and wind.
Each day gets a type: dry, wet, snowy or heavy, by freezing, cool or warm. Heavy means a lot of precipitation or snow.

How the expected value is worked out

For each day of the month we take the average on-time share of days of the same type outside that month.
The month’s expected value is the average of those. The range is an interval, built from the spread of days and the uncertainty of each average.
The observed value is the average of the same days, so the two are compared on identical days. It is "better" or "worse" only when outside the range.

When we say nothing

A type needs enough days of history, and most of the month’s days must have one. Otherwise the page says "not estimated yet".
Only days when both operators were fully captured count. Warnings and storms that ECCC issues are not in the daily record, so they are not used.

Số liệu đến từ đâu

Environment and Climate Change Canada, daily climate data (Open Government Licence - Canada)
Our observed on-time share, day by day

Phiên bản phương pháp và nhật ký thay đổi

Số liệu của một tháng đã công bố sẽ không bao giờ thay đổi. Nếu một phương pháp được sửa đổi, các tháng trước vẫn giữ phương pháp đã dùng để tính.

Phiên bản 1 · 28 tháng 10, 2026. First published. The on-time share we would expect for the month’s weather, from our own history, with a range.