Saint Clair, MO 63077 Weather

Key Messages

- Dry and seasonably warm conditions will persist through the weekend.

Short Term

Issued at 219 PM CDT Thu Oct 22 2026

A slow-moving upper-level ridge will dominate the Mid-Mississippi River Valley through the weekend with dry conditions continuing and only slight variations in above average temperatures. With a gradual exit of the surface high pressure center extending into the CWA this afternoon, the balance of airmass modification and subtle southeasterly low-level CAA through Friday followed by waves of upper-level clouds on Saturday and Sunday combined with weak southerly WAA will contribute to only slight fluctuations of high temperatures within the 70s F. Each night, the most favorable radiational cooling and coolest low temperatures in the 40s F will also become more and more confined to river valleys and southeastern MO/southwestern IL, closest to the high pressure and where clouds will be less prevalent and/or thinner. Patchy river valley fog is expected again Friday morning and potentially Saturday morning but coverage should be less.

Long Term

Issued at 219 PM CDT Thu Oct 22 2026

Global model guidance diverges considerably early to mid-next week in the evolution of an upper-level trough that propagates into the central CONUS Monday into Tuesday as the Omega Block breaks down. The track, amplitude, and tilt of this trough vary across guidance including whether an associated cold front passes through the CWA Tuesday or early Wednesday, enters and then stalls in the CWA, or stalls before reaching the CWA altogether. Accordingly, the NBM interquartile range increases to between 7 and 15 F Tuesday onward, with the 75th percentile remaining steady and the 25th percentile cooling closer to average. If the front reaches the CWA, showers will also become possible, with greatest probabilities of measurable rainfall in global ensemble models across central/northeastern MO and west-central IL at 30 to 50 percent. However, a widespread, substantial rainfall appears unlikely in the ranges of current scenarios. The aforementioned uncertainties persist through the end of the forecast period, late next week.

Aviation

Issued at 619 PM CDT Thu Oct 22 2026

Dry and mainly VFR conditions are expected through the period. There will be some fog late tonight into early Friday in low lying areas with MVFR and possible IFR visibilities including at SUS and CPS. Otherwise winds are expected to remain light.