Frost Risk Window by Brazilian Region

Frost dates by region: knowing when it's safe to plant

How much frost risk you face comes down to latitude, altitude and how close you are to the ocean. Down in southern Brazil the last spring frost usually lands somewhere between August and October, with the first autumn frost arriving from May to July, so the safe window to put cold-sensitive crops in the ground opens once that last frost has passed. Up in São Paulo's higher elevations, around Campos do Jordão and the Mantiqueira, you can still get frost anywhere from April to October. The southern climate lines up fairly closely with USDA zones 8–10. A radiative frost of −2 °C or below will scorch the tender leaves of tomato, basil and beans, along with most flowers, and during strong polar fronts advection frosts can push much further north than usual.

Applications

Planning a backyard or market garden, where you wait out the last frost before transplanting. Farming across southern and southeastern Brazil. Landscaping and ornamental planting. Fruit growing, since apples, grapes and peaches all need vernalization yet take a hit if their blossoms get caught. And knowing when to set off protection measures such as overhead irrigation, smudge pots or row covers.

FAQ

Is the calculator's date guaranteed? No. What it gives you is a climatological average. Any particular year can swing by weeks either way, so a short-range forecast from INMET or CPTEC should always win out over the historical norm.

Why does my low-lying garden frost more than the hilltop? Cold air is denser, so overnight it sinks and pools in valleys and dips in the land. The effect has a name: cold-air drainage. A site on a slope will usually shrug off the lighter frosts.

Do tropical regions ever frost? The Brazilian Northeast and the Amazon basin almost never do. The central plateau, the Cerrado, will occasionally get a light frost in its higher spots when a strong polar incursion comes through.