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Daily low

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GFS · Run 06Z 1 Oct · Valid Fri 9 Oct lowest of 4 × 6 h minima

Region Southwest
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The readings under the map are for the whole map, not only the part shown.

3030303030404040404040404040405050505050505050505050506060606060606060606060606060606060606060707070707070707080808080808080 89.5°20.8°

GFS · Run 06Z 1 Oct · Valid Fri 9 Oct lowest of 4 × 6 h minima

Mildest 89.5 °F · coldest 20.8 °F

The lowest temperature each point reaches over the whole of the day you choose.

Methodology

A day here runs 06Z to 06Z. The model files its minima in 6-hour blocks, so this is the lowest of 4 of them, and each column takes the 4 covering its own local day rather than one window for the whole continent. These are the model's own minima, so a low here can read a little colder than the same model's on a city's forecast, which is the coldest of its hourly values. The dashed line, when it appears, is 32 °F.

At six hours the blocks are coarser than the four and a half hours of solar time the map spans, so in practice almost every column lands on the same ones — the per-column choice is what keeps that true rather than lucky. It is the ECMWF map, over the nearer days where its blocks are finer, that changes the picture.

GFS. Of the four models on these pages, two file a daily extremum at all — GFS in 6-hour blocks; ECMWF in 3-hour blocks out to day 6 and 6-hour beyond. The other two publish temperature at instants, from which a daily low cannot honestly be recovered. The switch above draws the same day from the other one.

This map is drawn from model output we store ourselves, not from anyone's picture of it, and is based on data and products of NOAA. The per-city read of the same day — which cities the models are fighting about, and what the discussion makes of it — is on the national page.

Sources and licences

What we change: each field is cropped to the frame these maps share when we download it, and each map then smooths, contours, differences or ranks those numbers as its Methodology says. These are our maps of the providers' numbers, not their products, and none of them has reviewed or endorsed this site.

Coastlines, borders, lakes and place names: Natural Earth, public domain.