Think of a Jet stream as a fast-moving river of air. It is generally defined by wind speeds of 50 knots or greater with the strongest wind contained in the core of the jet stream. They form along boundaries between hot and cold air. Since these hot and cold air boundaries are most pronounced in winter, jet streams are the strongest and farther south during the winter. That also means jet streams are weaker and farther north in the summertime. Troughs will most likely have clear air turbulence as

💤 The jet stream is taking a nap: this animation shows how there will be a lack of jet stream action around NZ over the next 10 days... After frequently being located near the country during autumn, the polar jet has found itself buried deep in the Southern Ocean during winter as a La Niña-like pattern builds. The jet may strengthen in late July as the Madden-Julian Oscillation swings eastward from the Indian Ocean. >Ben | NIWA Weather

The weather is turning more unsettled, cooler and showery. But why does the jet stream have such an impact on our weather? | Met Office