Ottawa's changing climate

135 years of daily Environment Canada records for Ottawa — temperatures, extremes, precipitation and record events, updated automatically.

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135 years, at a glance

Each stripe is one year's average temperature, colour-coded from the coldest to the hottest year on record. Hover a stripe for the year and value.

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Annual mean temperature

Yearly average temperature (thin line) with a 10-year rolling average (bold line) to see past the year-to-year noise.

The shape of a year

Each ring traces one year's daily mean temperature, drawn clockwise from Jan 1 at the top — distance from the centre encodes the temperature. The current year draws day-by-day in full colour; every year already drawn stays on the chart as a faint trace, tinted by that year's overall warmth (same colour scale as the stripes above), so the shape's drift over 135 years builds up in front of you.

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Warming isn't even across seasons

Mean temperature by season, each with its own trend line. Winters typically warm fastest — worth checking against Ottawa's own record.

Hot extremes are up. Cold extremes are down.

Count of days per year hitting each threshold. This is the honest "extreme weather" story: not a flat increase in all extremes, but a shift in which kind occurs. Click a legend item to isolate a line.

The snow-to-rain shift

Rain's share of total precipitation (by water-equivalent volume) — a rising line means winters are trending toward more rain and less snow.

Recent extremes, hour by hour (1953–present)

Wind, humidex and wind-chill only exist at hourly resolution, so this record is shorter than the 1889 daily one — but still 70+ years. Hot/tropical are shown as hours here, not days — the same underlying threshold as the daily chart above, but counting actual duration instead of just whether a day tipped over the line at all.

Hourly precipitation amount is not usable here — it's essentially unrecorded for this station in every decade checked, 1953–present — so no rainfall-intensity index is shown. Precipitation totals above come from the daily record instead.

Max wind speed is the station's own hourly reading, not a storm-chasing measurement — it won't catch a tornado unless the funnel happens to pass directly over the sensor. The Sept 21, 2018 Ottawa–Gatineau EF3 tornado, for example, shows up as an unremarkable 50 km/h that hour: the touchdown path was several km from the station, and an hourly-averaged reading smooths out anything that lasts only seconds to minutes anyway. Station wind records are a poor instrument for tracking tornado trends — that needs damage-survey data, which this dataset doesn't have.

Lightning strikes (2021–present)

Actual strike counts, not just thunderstorm-day counts — from a different, non-ECCC source with a much shorter record. Read the caveat below before drawing a trend from this one.

Strikes per year — Ottawa region

Days per year with any lightning

Which months get the lightning

Time of day (approx. Ottawa local)

Records & extremes

The single most extreme readings on record — and how the whole climate has shifted underneath them. All-time temperature, snow and rain records come from the full daily history (1889+); humidex, wind chill, wind speed and the hour-by-hour leaderboards only exist in the shorter hourly record (1953+).

A warming climate, in the record books · 30-yr normals: — vs —

All-time records

Longest streaks

Leaderboards

Pick a year you remember

See how that year's climate compares to the most recent complete year on record.

YEAR vs. most recent complete year (—)

Data & methodology

Source: Environment and Climate Change Canada, climate.weather.gc.ca (public, no API key).

Daily record (1889–present): Ottawa CDA station, which is still active today; a modern airport station only fills specific missing days, never a wholesale switch-over.
Hourly record (1953–present): the historic Ottawa Macdonald-Cartier Intl A station (1953–2011) handing off to the modern station (2012–present).
Thresholds used: hot day/hour ≥ 30 °C, extreme cold ≤ −25 °C, tropical night/hour ≥ 20 °C (tropical hours counted 21:00–05:59), heavy-rain day ≥ 25 mm, high-wind hour ≥ 50 km/h, extreme humidex ≥ 40, extreme wind chill ≤ −35.
Thunderstorm severity: ECCC's hourly weather-condition text distinguishes plain "Thunderstorms" from storms tagged "Hail" or "Heavy Thunderstorms" — a day only counts as severe if one of those stronger tags appears. A bare thunderstorm flag alone says nothing about intensity, so both are shown separately rather than lumped together.
A year is only plotted in full-record trend lines once it has enough valid observations to be considered complete (partial start/current years are excluded from trend statistics, though shown where noted).