The coolest temperatures since spring are finally on the way. See how far they will drop

Anna Moneymaker/Getty Images

The atmosphere’s attempts to make it feel actually like fall across much of the United States have been repeatedly thwarted in recent weeks, but that’s about to change in a major way.

Temperatures will plummet to their lowest levels since spring for many east of the Rockies later this week as a potent cold front slices across the country.

The dramatic pattern flip won’t come a moment too soon for some still roasting under summerlike heat: Dozens of locations in the central and southern US will soar to record high temperatures on Tuesday, but the incoming front will drag those highs down by more than 30 degrees in many locales by Friday or Saturday.

Some spots in the northern US this weekend could flirt with freezing temperatures overnight for the first time since spring, too. The cold front could also ramp up a multi-day flood threat in the Plains and Texas.

Things will have to get worse before they get better. Summerlike heat will peak Tuesday in the central US, with highs in the 90s forecast as far north as Illinois and Indiana, and 80s through the Ohio Valley.

St. Louis could experience its hottest day this late into the year when it soars into the mid-90s Tuesday. Detroit and Cleveland are forecast to top out in the 80s and could break their high temperature records for the date.

The heat will ease only slightly on Wednesday as the front starts to impinge on the central US, but the South will continue to swelter under widespread temperatures in the upper 80s and low 90s.

Atlanta could challenge its record high for the date of 87 degrees Fahrenheit on Wednesday. The same goes for Nashville’s record of 89 degrees Fahrenheit.

Thursday will be another hot day for the Southeast and south-central US, but the big temperature swings will begin in the Plains and parts of the Upper Midwest as the cold front continues its slow journey east.

Kansas City, Missouri, could max out in the mid 70s on Thursday after topping 90 degrees Fahrenheit Tuesday — a nearly 20-degree reversal.

The turnaround kicks in even more Friday, when highs in the 50s and 60s are forecast from the Plains to the Midwest and Ohio Valley.

St. Louis may only reach the low 60s — more than 30 degrees cooler than Tuesday’s likely record-breaking temperature. That would also mark the city’s coolest day since early May.

Chicago is in the same boat: Its high temperature is also expected to be nearly 30 degrees cooler than Tuesday and its forecast high in the lower 50s would mark the chilliest day since early May.

Fall finally comes for all of the East Coast and South on Saturday as the front reaches the coast. Highs in the 60s and 70s are expected in the South, while the Great Lakes and Northeast only top out in the 50s or 40s.

Selcuk Acar/Anadolu/Getty Images

New York City could barely hit the low 50s on Saturday, meaning it’ll likely be the coolest day since late April. Washington, DC, will also have its coldest day since late April, with its high expected to max out in the mid-50s.

Atlanta will peak in the upper 60s. That would have marked the coolest day since early May if not for the rainy, windy and cool day former Hurricane Isaias created last Saturday. But the city will definitely hit its coldest overnight low since spring by early Sunday morning , when the temperature dips below 50 degrees Fahrenheit.

Sunday will also mark the coldest morning since spring in Nashville, Dallas, New York City, Washington, DC, and many other locations.

The cooldown won’t be very long-lived as unseasonable warmth is likely to return next week.

The coming fall weather will bring a streak of danger to the central US midweek. Deep tropical moisture flowing from the Gulf will slam against the cold front when it’s draped over the Plains and fuel a multi-day flood threat. Storms could also train, or move repeatedly move over the same areas like train cars on a railroad track.

Wednesday and Thursday are the days with the most flood concern, but some issues could begin as early as Tuesday evening.

Scattered severe thunderstorms could also fire up near the cold front late Tuesday afternoon or in the early evening. Damaging winds and hail will be the main threats, but an isolated tornado is possible.

The areas most at risk of flooding are also still dealing with serious drought conditions. The rain is much-needed, but flash flooding is possible if it falls faster than the dry ground can absorb.

The flood risk will diminish Friday as the front starts to move east.

安娜·莫尼梅克/盖蒂图片社

最近几周，美国大部分地区的大气试图营造出秋天的氛围，但屡屡受挫，不过​​这种情况即将发生重大改变。

本周晚些时候，一股强劲的冷锋将横扫全国，落基山脉以东许多地区的气温将骤降至春季以来的最低水平。

对于一些仍在酷暑中煎熬的地区来说，这种戏剧性的天气模式转变来得正是时候：周二，美国中部和南部数十个地区的气温将飙升至历史新高，但即将到来的锋面将在周五或周六将许多地区的最高气温拉低 30 多度。

本周末，美国北部部分地区夜间气温可能接近冰点，这将是自春季以来的首次低温。冷锋还可能加剧平原地区和德克萨斯州持续数日的洪涝灾害风险。

情况必须先恶化才能好转。美国中部地区周二将迎来酷暑，预计伊利诺伊州和印第安纳州北部最高气温将达到90多华氏度（约32摄氏度），俄亥俄河谷地区最高气温也将达到80多华氏度（约27摄氏度）。

圣路易斯周二气温可能飙升至90多华氏度，有望迎来今年以来最热的一天。底特律和克利夫兰的最高气温预计也将达到80多华氏度，并可能打破当日最高气温纪录。

周三，随着锋面开始影响美国中部地区，高温天气只会略有缓解，但南部地区仍将持续酷热，普遍气温将达到 80 多华氏度到 90 多华氏度。

亚特兰大周三可能挑战当日最高气温纪录87华氏度。纳什维尔也有可能挑战当日最高气温纪录89华氏度。

周四美国东南部和中南部地区将再次迎来炎热天气，但随着冷锋继续缓慢向东移动，平原地区和中西部北部部分地区将开始出现大幅气温波动。

密苏里州堪萨斯城周四最高气温可能在 70 华氏度左右，而周二气温超过了 90 华氏度——气温下降了近 20 度。

周五气温将进一步回升，预计从平原地区到中西部和俄亥俄河谷，最高气温将达到 50 到 60 华氏度。

圣路易斯的气温可能只有60华氏度左右——比周二可能打破纪录的气温低30多度。这也将是该市自5月初以来最冷的一天。

芝加哥的情况也一样：预计其最高气温也将比周二低近 30 度，预计最高气温在 50 度左右，这将是自 5 月初以来最冷的一天。

随着冷锋抵达海岸，美国东海岸和南部地区将于周六正式迎来秋季。南部地区最高气温预计在60至70华氏度之间，而五大湖区和东北部地区最高气温仅为50至40华氏度。

塞尔丘克·阿卡尔/阿纳多卢/盖蒂图片社

纽约市周六气温勉强达到华氏50度左右，这意味着这将是自四月下旬以来最冷的一天。华盛顿特区也将迎来自四月下旬以来最冷的一天，预计最高气温在华氏50度左右。

亚特兰大最高气温将接近华氏60度（约摄氏16度）。如果不是上周六飓风伊萨亚斯带来的阴雨、大风和凉爽天气，这将是自五月初以来最凉爽的一天。但到周日清晨，亚特兰大的最低气温肯定会降至华氏50度（约摄氏10度）以下，这将是自春季以来最冷的夜间气温。

周日，纳什维尔、达拉斯、纽约市、华盛顿特区和许多其他地方将迎来自春季以来最冷的早晨。

这波降温不会持续太久，因为下周很可能再次出现反常的温暖天气。

即将到来的秋季天气将给美国中部地区带来一股危险，预计本周中期到来。来自墨西哥湾的深厚热带湿气将与笼罩平原地区的冷锋相遇，引发持续数日的洪涝灾害。风暴还可能像火车车厢在铁轨上一样，反复经过同一区域。

周三和周四是洪水风险最高的日子，但有些问题最早可能在周二晚上就开始出现。

周二下午晚些时候或傍晚时分，冷锋附近可能出现零星强雷暴。破坏性大风和冰雹将是主要威胁，但也不排除出现零星龙卷风的可能性。

最易受洪水侵袭的地区目前仍面临严重的干旱。虽然急需降雨，但如果降雨速度超过干燥土壤的吸收能力，则可能引发突发性洪水。

随着锋面开始东移，洪水风险将于周五降低。