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Rapid Arctic warming is hypothesized to favor an increased persistence of regional weather patterns in the Northern Hemisphere (Francis & Vavrus, 2012). Persistent conditions can lead to drought, heat waves, prolonged cold spells, and storminess that can cost millions of dollars in damage and disrupt societal and ecosystem norms. This study defines a new metric called long-duration events (LDEs)-conditions that endure at least four consecutive days-and takes two independent approaches to assessing seasonal changes in weather-pattern persistence over North America. One applies precipitation measurements at weather stations across the United States; the other is based on a cluster analysis of large-scale, upper-level atmospheric patterns. Both methods indicate an overall increase in LDEs. We also find that large-scale patterns consistent with a warm Arctic exhibit an increased frequency of LDEs, suggesting that further Arctic warming may favor persistent weather patterns that can lead to weather extremes.

Plain Language Summary Rapid Arctic warming and sea ice loss are expected to affect weather patterns around the Northern Hemisphere. An increased persistent of weather regimes is one hypothesized impact. Long-lasting weather conditions can lead to destructive extreme events, such as droughts, prolonged cold spells, heat waves, and flooding. This study uses daily precipitation measurements across the United States, as well as daily large-scale atmospheric patterns over the eastern Pacific and North America, to assess changes in weather-regime persistence and whether any changes are associated with a rapidly warming Arctic. We find an increased frequency in long-lived patterns in recent decades, especially those with abnormally warm high latitudes, suggesting that further Arctic warming may favor an increase in extreme events caused by prolonged weather conditions.