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This study investigates the seasonality of near‐surface wind speeds associated with extratropical cyclones (ETCs) over northeastern North America using a global reanalysis data set during 1979–2020. As opposed to most studies that emphasize winter storms, ETCs during the fall exhibit significantly stronger 10‐m winds over this region due to the slightly stronger continental cyclones and significantly weaker low‐level stability during that time of the year. Also, ETCs favor inland lakes and Hudson Bay during the low‐ice‐content fall season, leading to lower surface roughness. Combining these results, we derive simple linear regressions to predict the 10‐m wind speed given three variables: 850‐hPa wind speed, low‐level Richardson number, and surface roughness length. This formula captures the observed seasonality and serves as a valuable tool for cyclone near‐surface wind risk assessment. Plain Language Summary: Extratropical cyclones can bring powerful winds that can cause severe damage to infrastructure. We find that cyclones with severe winds are the most frequent in the fall season over continental northeastern North America. Three reasons are found responsible: stronger continental cyclones, weaker low‐level atmospheric stability, and the lower surface roughness over lakes and Hudson Bay, where cyclones frequently occur in fall. A simple formula that can effectively assess the near‐surface wind speeds associated with cyclones is derived based on these results. Key Points: Extratropical‐cyclone‐associated 10‐m wind speeds are the strongest in the fall season over northeastern North AmericaBesides stronger continental cyclones and 850‐hPa winds, weaker low‐level stability in fall favors stronger 10‐m wind speeds in this regionLinear regression using 850‐hPa wind, Richardson number, and surface roughness well predicts cyclones' 10‐m wind speeds and seasonality [ABSTRACT FROM AUTHOR]

We quantify GIA prediction uncertainties of 250 1D and 3D glacial isostatic adjustment (GIA) models through comparisons with deglacial relative sea‐level (RSL) data from North America and rate of vertical land motion (U̇) and gravity rate of change (Ġ) from GNSS and GRACE data, respectively. Spatially, the size of the RSL uncertainties varies across North America with the largest from Hudson Bay and near previous ice margins along the northern Atlantic and Pacific coasts, which suggests 3D viscosity structure in the lower mantle and laterally varying lithospheric thickness. Temporally, RSL uncertainties decrease from the Last Glacial Maximum to present except for west of Hudson Bay and the northeastern Pacific coast. The uncertainties of both these regions increase from 30 to 45 m between 15 and 11 ka BP, which may be due to the rapid decrease of surface loading at that time. Present‐day U̇ and Ġ uncertainties are largest in southwestern Hudson Bay with magnitudes of 2.4 mm/year and 0.4 μGal/year, mainly due to the 3D viscosity structure in the lower mantle. Key Points: We predict the GIA signal with uncertainties of RSL and present‐day U̇ and Ġ in North America that are associated with 3D structuresGIA‐predicted RSL uncertainties are largest around Hudson Bay and near former ice margins along northern Atlantic and Pacific coastsThe maximum uncertainties of present‐day U̇ and Ġ are centered in southwestern Hudson Bay and near former ice margins [ABSTRACT FROM AUTHOR]