METARs and TAFs: What's Different in Canada (And What the INRAT Tests)

Canada uses full ICAO-format METARs and TAFs — the same standard as most of the world, and different in a few key ways from what older American pilot training materials describe. If you learned on US-focused resources, some of what you know may not apply directly. Here's what actually shows up on the INRAT.

A real Canadian METAR, decoded

Let's start with an example:

CAVOK — the most tested Canadian METAR code

CAVOK (Ceiling And Visibility OK) replaces the visibility, weather, and cloud groups when all three of the following conditions are met:

• Visibility is 6 statute miles (9 km) or greater
• No cloud below 5,000 feet AGL and no cumulonimbus at any height
• No significant weather (no precipitation, fog, or other significant phenomena)

CAVOK is extremely common in Canadian TAFs during good weather periods. On the INRAT, a question might give you a TAF with CAVOK and ask about the forecast ceiling or visibility — the answer is that no ceiling is forecast below 5,000 ft and visibility is at least 6 SM. Don't overthink it; CAVOK is a convenient "all clear" indicator.

Reading TAFs: BECMG, TEMPO, and PROB

Canadian TAFs are 24- or 30-hour forecasts issued by NavCanada's Meteorological Service. The change groups are the part that trips people up:

• BECMG (Becoming) — gradual change expected to be completed within the specified period. Example: BECMG 1416 18010KT means between 1400Z and 1600Z, wind will gradually change to 180° at 10 knots and remain so afterward.
• TEMPO (Temporary) — temporary fluctuations expected to last less than one hour at a time and occur during less than half the time period. Conditions revert to the prevailing forecast after each occurrence.
• PROB30 / PROB40 — probability of 30% or 40% that the specified conditions will occur. PROB30 means less likely; PROB40 means moderately likely. These are often combined with TEMPO: PROB30 TEMPO 1416 +TSRA.

The INRAT will give you a TAF excerpt and ask whether alternate requirements are triggered (see CARS 602.122), or what conditions to expect at a specific time. Work through TAF change groups in sequence — each group overrides the previous prevailing conditions until the next change group.

NOSIG and other Canadian-specific codes

NOSIG (No Significant Change) appears at the end of a METAR when no significant change in conditions is expected within the next two hours. It's a short-term forecast appended to an observation — not a full TAF. Useful for departure planning but don't rely on it for destination weather at a distant ETA.

RMK (Remarks) — Canadian METARs include a remarks section. Common remarks: SLP (sea level pressure in hectopascals), PRESRR/PRESFR (pressure rising/falling rapidly), and cloud-type identifiers like CB (cumulonimbus) or TCU (towering cumulus). The INRAT occasionally tests RMK codes, particularly SLP and pressure trend indicators.

What the INRAT specifically tests

Most METAR/TAF questions on the INRAT do one of three things:

1. Extract conditions — given a METAR, determine ceiling, visibility, or weather type. Straightforward if you know the format.
2. Alternate determination — given a TAF, determine whether conditions trigger the alternate requirement under CARS 602.122. Apply the threshold: ceiling below 1,000 ft above lowest approach minimum, or visibility below 3 SM, within ±1 hour of ETA. These thresholds connect directly to the broader topic of IFR weather minimums in Canada.
3. Change group interpretation — given a TAF with BECMG or TEMPO, determine what conditions apply at a specific time. The majority of candidates who miss these questions do so because they misread which conditions are prevailing vs temporary.