Update (4:08 p.m. Wednesday, July 20):

Cooler air should arrive in Ames sooner than expected. The National Weather Service in Des Moines has shortened the length of the excessive heat warning that has been in effect since noon Sunday. The warning now expires at 4 a.m. Thursday instead of 9 p.m.

As of 3:53 p.m., the temperature at the Ames Municipal Airport was 95 degrees and the heat index was 107.

The latest update says high temperatures this afternoon and early evening will remain in the mid to upper 90s. Heat index readings could range from 105 to near 120 degrees. Temperatures are expected to fall into the low to mid 70s overnight, with the heat index ranging from 80-85 degrees. A cool off is expected by early Thursday morning.

The weather services forecast for Thursday calls for a mostly cloudy day with a high near 87 and a 50 percent chance of showers and thunderstorms.

 

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Update (8:17 a.m. Wednesday, July 20)

An excessive heat warning remains in effect until 9 p.m. Thursday.

Temperatures are expected to rise into the mid to upper 90s Wednesday afternoon before dropping slightly for Thursday. Overnight lows are expected to be in the mid to upper 70s each night.

The heat index for Wednesday is expected to be between 112 and 118 degrees.

An increasing chance of thunderstorms begins early Thursday morning and continues through Saturday. Cloud cover from this system should lower heat index temperatures to the 105 to 110 degree range on Thursday, according to the weather service.

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Update (3:31 p.m. Saturday, July 16):

The National Weather Service in Des Moines has extended the excessive heat warning through 9 p.m. Thursday. Afternoon high temperatures are expected to reach the lower to middle 90s through next Thursday. Night temperatures are expected to only fall into the mid to upper 70s. Humidity will produce heat index temperatures from 100 to 115 degrees in the afternoon and around 80 degrees at night. 

 

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Update (3:45 p.m. Friday, July 15):

The National Weather Service in Des Moines has upgraded the alert from a watch to a warning. An excessive heat warning will now be in effect from noon Sunday, July 17 through 7 p.m. Wednesday, July 20.

On Sunday temperatures are expected to reach into the lower 90s. Temperatures Monday through Wednesday are expected to reach into the mid 90s. Little overnight relief is expected, with temperatures only falling to the mid 70s. High humidity will push the daytime heat indices into the 100-115 degree range, and keep the heat indices near 80 overnight.

 

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Update (8:12 a.m. Friday, July 15):

The National Weather Service in Des Moines has extended the exessive heat watch through Wednesday afternoon. High temperatures in the upper 90s and heat indices in the 100-110 range are expected to begin on Sunday and continue through Wednesday evening.

 

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The National Weather Service in Des Moines has issued an excessive heat watch for the area. The watch is in effect Sunday afternoon through Tuesday evening.

The watch says that a “large upper level ridge of high pressure will build into the upper Midwest by the weekend and remain in the region into next week. Under the high pressure ridge hot and humid weather is forecast.”

Temperatures are expected to reach the lower to middle 90s on Sunday and the upper 90s on Monday and Tuesday. Overnight lows will remain in the mid to upper 70s. The heat index will be between 100 and 110 degrees each afternoon and the upper 70s to low 80s each night.

The weather service warns that “several days of excessively high heat and humidity with little relief at night can cause significant stress on individuals and create conditions favorable for heat related problems.”

The watch advises drinking plenty of fluids, staying in an air-conditioned room and staying out of the sun.