Where the weather models disagree on lows in Chicago

The models are the independent global centres Open-Meteo serves for this point — GFS, ECMWF IFS, ICON, GEM, UKMO and the AIFS and AIGFS AI models — as The Spread recorded them at its last sweep. NBM and every other blend are left out: a consensus product hides the disagreement this page exists to show.

Each model publishes to a different horizon, which is why Models is counted per day rather than once. Beyond day 14 only two models remain and both are NOAA's, so the page stops there. Range is the lowest to the highest model low; Spread is the gap between the coolest and warmest model.

A model's low is the coldest temperature it forecasts for that calendar day, midnight to midnight local time. That is usually the morning's low; behind a cold front arriving late in the day it can be the evening's instead.

Typical spread is the median spread for that lead over the last month here, and needs ten days of forecasts at that lead before it is shown. It is there because a wide band ten days out is ordinary and the same band tomorrow is not — so nothing on this page is called a divergence; the comparison is against what this lead usually looks like at this location.