The second heatwave of the summer is settling in across portions of the region, and will be affecting portions the state today through mid-week.
Areas near the St. Louis metro area urban heat island have had high temperatures well into the 90’s the past few days, but of focus is the more widespread and hotter temps into the 90’s for a larger portion of the state today through mid-week. Several consecutive days with high temps in the 90’s is likely across portions of Central and Southern Illinois. Overnight low temps will likely remain well into the 60’s and 70’s during this period. High temps in the St. Louis metro area are likely to be in the upper 90’s to near 100 for severel days during this period. Further north across other portions of Central and Northern Illinois, a day or two of temps near or into the 90’s is possible, but conditions ill be better than further south.
With several days of hot temps into the 90’s expected for portions of Central and Southern Illinois and moisture values at moderate to high levels, heat indices will likely reach up to around 100 for many areas for a good portion of the period, with some potential for values up to around 105. The combination of duration and potential for high heat index values for several days, could lead to oppressive conditions for some areas. At this time it does not appear that any records will be in jeopardy of being broken though.
It should be noted that there will be daily chances for thunderstorms, first farther north early in the week, eventually extending south as the week goes on. This activity and associated cloud debris could help temper the heat for some areas.