The July Outlook

July is the most stable and predictable period in the year. Eighty-five percent of all the days reach above 80 degrees (35 percent in the 90s, fifty percent in the 80s). The average highs and lows vary only one degree in the entire month. Temperatures reach above 100 two percent of the time (although record highs above 100 have been recorded for almost every afternoon this month). Only ten percent of the next 30 days provide the likelihood for highs in the 70s, and 60s come just twice in a decade.

In most years, the warmest days of the month are July 8th, 9th, 10th, 16th, 17th, 18th, 19th, 20th, 21st, 25th, 26th, and 28th. Normal average temperatures usually fall one degree in the wake of the final July weather system, the first drop since late January, and the first of the thermometer's many steps to winter.
An average of two to four inches of rain, most of it carried in seven or eight thunderstorms, typically falls between the last of June and the first of August. Precipitation is most common during the first 13 days of the month and at the beginning of the fourth week.

The wettest days of middle summer are July 2nd, 3rd, (the very wettest days), and 4th, 8th, 10th, 11th, 12th, 13th, 21st, 22nd, 23rd, 24th, 25th, and 26th, all of which have a 40 percent or better chance for precipitation. Of those rainy days, the cloudiest are July 2nd, 12th, 13th, 22nd, and 26th.
There are usually between three and five days each week suitable for fieldwork. The percentage of sunshine likely to be experienced on any July day is 70 percent. The driest days, those with less than a 20 percent chance of rain are July 6th, 16th, 17th, and 18th. The sunniest days are the 7th, 10th, 16th, 17th, 18th and 29th.

WEEKLY WEATHER
WEEK 1
Although clouds are relatively rare through the end of June, they suddenly become more frequent on the 1st and 2nd of July. Then, starting on the 3rd, the sun returns (between showers), and remains through the 11th. Temperatures are generally a little cooler than those of the previous week: the chance for 80s or 90s falls from 80 percent down to about 60 percent. Chances for rain and humidity, however, are considerably higher in the first two weeks of July than in the last two.

WEEK 2
The Corn Tassel Rains, which typically begin at the end of June, continue through the period, and temperatures, which cooled somewhat during the first days of July, begin to grow warmer. After the 7th, there is a full 90 percent chance that afternoon highs will reach 80 or above. July 7th through the 9th are some of the worst Dog Days of the year, all three bringing a ten percent chance for heat above 100 degrees. Still, the period between July 13th and 15th brings cooler conditions in the 70s twenty-five percent of the years, with the 13th being known to see a high just in the 60s. Nighttime lows typically remain in the 60s, but chilly 50s occur an average of 15 percent of the time.

WEEK3
Temperatures are in the 80s and 90s most of the time this week, and highs above 100 are more likely to occur on July 15th and 16th than any other days of the Midwestern year (a fifteen percent chance for such heat). Nighttime lows typically remain in the 60s, but chilly 50s occur an average of ten to 15 percent of the time. Rain is a bit more likely this week than it was last week as chances for showers rise over the next seven days from between 20 and 30 percent to between 35 and 40 percent.

WEEK4
The coolest days of the week are typically the 22nd and 23rd of the month, when mild 70s are recorded about a fourth of all the years. The 23rd brings cool sleeping conditions more often than any night in July: a full 35 percent of the nights drop below 60 degrees. The most consistent day of the period, and of the whole month, is the 24th when highs in the 80s come 95 percent of the time. Sunshine remains the rule for this week of the month, with three out of four days bringing at least a partial break in the clouds. Chances for rain typically decline as July comes to a close, dropping from 40 to 45 percent on the 24th down to just 20 percent on the 30th and 31st. A cool front sweeps across the country between the 27th and the 29th. Five years in ten, at least one afternoon in the 70s follows that late-July cool wave. Evening lows in the 50s, unusual only two weeks ago, often occur. And average high temperatures drop one degree on the 28th, their first drop since late January.

SUMMERCOUNT
Between the last week of May and the first week of September, 14 major cool fronts of summer cross the United States. One of those weather systems developed in May, five in June, and July brings four more. Summer fronts will reach the lower Midwest around the following dates; they will come through about two days earlier in the West, a day or two later in the East.

July 6: The front of July 6th is usually associated with the Corn Tassel Rains, and Dog Day heat. Thunderstorms typically precede this weather system, sometimes bringing hail.

July 14: The July 14th front—unlike the previous front—is associated more with drought than with rain. Often, the Dog Days intensify after the passage of this weather system. Pastures, field crops, lawns, and gardens become stressed from heat and lack of rain.

July 21: This front is typically stronger than the first two of July, and brings the best chance since the Corn Tassel Rains for a shower on the crops and maybe slightly cooler weather.

July 28: The last front of July is not known for its vitality. Ordinarily, it moves across the country with little precipitation or significant change in temperatures.

THE DAILY WEATHER HISTORY
July 1
Today brings highs in the 90s twenty-five percent of the time, 80s fifty percent, 70s the rest. Rain falls 40 percent of the days, and skies are completely overcast one third of all the years.
July 2
The likelihood of rain increases from 40 percent to 55 percent today as the Corn Tassel Rains intensify. The sky becomes overcast almost half the years. Highs reach to the 90s once or twice in a decade; the rest of the years are pretty evenly divided between 70s and 80s.
July 3
Today’s high temperature distribution: 90s thirty percent, 80s fifty percent, 70s twenty percent. The sun shines eight years in a decade on this date, but showers pass through 60 percent of the time. Thunderstorms push the nighttime lows into the milder 50s thirty-five percent of the years.
July 4
The Dog Star brings an afternoon in the 90s forty-five percent of the time on this date – the highest percentage of 90s so far in the year. Eighties occur forty percent of the days, 70s fifteen percent. Skies are clear to partly cloudy eight to nine days in ten, but showers pass through four years in a decade. Nighttime temperatures are generally in the 60s, with 50s occurring only 15 to 20 percent of the time.
July 5
There is a 30 percent chance for highs in the 90s today, 55 percent for 80s, fifteen percent for 70s. The skies are partly sunny nine years out of ten, but showers pass through one day in three. Nighttime lows are in the 60s or 70s ninety percent of the time.
July 6
This is typically the driest day in the first two weeks of July. Showers fall only 25 percent of all the years. Cool temperatures in the 70s can be expected 35 percent of the time, but 80s come on 20 percent of the years, and 90s on 45 percent. Lows in the 50s occur on a third of the nights, 60s and 70s on the rest.
July 7
Today's temperature distribution: 70s on 25 percent of the afternoons, 80s on 30 percent, 90s on 40 percent, and 100s on five percent. Morning lows are the 50s half the time, so the night of July 6th - 7th is one of the more pleasant July nights for sleeping. The sky is clear to partly cloudy 95 percent of the time, making July 7th the brightest day of the month. Thunderstorms, however, are not uncommon; one year in three brings rain today.
July 8
Today is a classic Dog Day, with heat, humidity, sun, and an occasional thundershower. Fifty percent of the highs are in the 80s, thirty-five percent in the 90s, and the chance for a high of 100 is five to ten percent – the same chance as for cool 70s. The sky is mostly sunny 75 percent of the time; showers pass through four years in ten. A cool night in the 50s occurs less than twice in a decade.
July 9
There is a ten percent chance for temperatures of 100 or above, 35 percent for 90s, fifty percent for 80s. Rain falls half the days in my record, but the sun appears nine years in ten. Most nights are warm : 95 percent of them are in the 60s or 70s. And tonight begins a two-week period during which lows in the 50s occur less frequently than at any other time of the year.
July 10
The likelihood of a high in the 90s today is 45 percent, with another 45 percent for 80s, and ten percent for 70s. The sun appears 90 percent of the days, but showers occur almost one day in two. Nights are typically warm, mild 50s occurring only once in a 15 years.
July 11
Chances for rain are 40 percent today, but the sun appears nine days in a decade on this date. Highs in the 90s occur 25 percent of the time; 80s come six days in ten, and the chances for a milder afternoon in the 70s remain at 15 percent. Tonight is the third night in a row during which chances for a low in the 50s are only between five and ten percent.
July 12
Skies are totally overcast 30 percent of the time, and rain can be expected five years in ten. The temperature distribution is usually identical to that of the 11th: mostly 80s and 90s with a slight chance for 70s. Lows in the 50s, however, come twice as often as on the 11th, but that still only means that ten to 15 percent of the nights are so cool.
July 13
Even though the average temperature distribution for this date is close to that of the previous two days (25 percent chance for 90s, 55 percent for 80s, 15 percent for 70s), highs never made it out of the 60s back in 1990, a rare occurrence in an Ohio July (odds are about 100 to one against it). The 13th is one of the rainiest days of July - sharing that position with July 1st and 2nd - and carrying a 55 percent chance for a thunderstorm. Overcast conditions are also relatively common on this date, recorded a little more than one day out of every three.
July 14
Highs rise into 90s on 45 percent of the afternoons, are in the 80s on 40 percent, in the 70s the remaining 15 percent. Totally overcast conditions dominate today’s weather just one day in four. Rain comes one day in three, with hail a slight (one to two percent) possibility. Morning lows in the chilly 50s occur ten to fifteen percent of the years.
July 15
Highs above 100 occur ten to 15 percent of the time today and tomorrow, the only two days of the year on which temperatures rise so high so often in the lower Midwest. Nineties occur 20 percent of the years in my record, 80s forty to 45 percent, 70s twenty-five percent of the time. Skies are overcast only one year in five, and a thunderstorm develops just one in four. In spite of the increased possibilities for 100s today, early morning temperatures fall into the mild 50s twenty percent of the time, a relatively high percentage for the second and third weeks of July.
July 16
Today is one of the hottest, sunniest, and driest days in the whole year. Highs above 100 come 15 percent of the time; 90s are recorded 25 percent of the time; 80s occur on 55 percent of the days, 70s just five percent. The sky is typically sunny to partly cloudy, with completely overcast conditions recorded just five percent of the days. Rainfall on the 16th occurs on fewer than 20 percent of all the years.
July 17
The 17th typically has fewer clouds than almost any other day of the entire year. And it is normally free from precipitation: this is the second day of a three-day dry spell during which the chance of rain continues at 15 percent. Highs reach into the 90s forty-five percent of the time, to the 80s another 45 percent, and to the 70s just ten percent.
Average temperatures in the lower Midwest reach their peak today with highs at 85 and lows at 65. Averages remain at that level through the 28th of the month, after which they begin their autumn descent. The coldest averages of the year remain steady for a similar period, reaching a normal high of 34 and a normal low of 18 on January 16th, starting their rise to summer on January 29th.
July 18
July 18th is almost always a Dog Day par excellence. Temperatures climb above 90 degrees 50 percent of the time, more often than during any other 24 hour period of the year. Highs in the 80s occur on 45 percent of the afternoons, with cool 70s coming just five percent. A thunderstorm moves across the area one year in five, and the sky is clear to partly cloudy 95 percent of the time.
July 19
Today is one of a handful of days on which the chance of a high below 80 degrees is less than five percent: about 45 percent of the afternoons are in the 90s, and the other 55 percent in the 80s. The likelihood of rain increases from 20 to 30 percent, and odds for a completely cloudy day are one in four.
July 20
Highs in the 70s are recorded just five percent of the afternoons; 80s come 55 percent of the time, 90s thirty-five percent. Today is one of the early pivot points in the progress toward winter: it is the last day of the year on which 100 degree temperatures have a five to ten percent chance of occurring. Showers come 35 percent of all the years.
July 21
High temperatures are above 90 four days in ten, between 80 and 89 five days in ten, in the 70s one in ten. Even though record lows dip into the upper 40s in the Midwest, morning lows almost never reach below 60 on this date. Chances for rain are 40 percent, for completely overcast skies 30 percent.
July 22
Afternoons in the 90s are recorded 35 percent of the years on July 22nd, and 80s come 40 percent. Cool 70s occur on 25 percent of the years, the highest likelihood for moderation since July 11th. Chances for rain are almost 50 percent, with completely overcast conditions occurring 40 percent of the days.
July 23
Today has a temperature distribution identical to that of the 22nd, and the chances for rain continue at near 50 percent; sky conditions, however, are usually less cloudy: the sun shines at least 95 percent of the time. Thanks to the cool wave that often comes through this time of year, there is a 40 percent chance for a low in the 50s, making this the coolest morning since the beginning of the Corn Tassel Rains. Although moderate nights do not stay for long, today could be considered one of the first meteorological signs of deterioration in the power of summer.
July 24
Today is almost always in the 80s: there is an 85 percent chance of that, and almost no chance for 70s. Heat in the 90s occurs just 15 percent of the time, the lowest incidence of such heat since June 28th. That is an indication of the residual power of the third major high-pressure system; it is also another minor step on the road to winter. Rainfall is typically common on the 24th: four days in ten bring a shower on this date. But the sun shines on eight or nine days out of ten.
July 25
As the third cold wave of the month moves out over the Atlantic Ocean, oppressive conditions are common on the 25th in the lower Midwest. Highs reach 90 on 45 percent of all the afternoons. Eighties take up the other 55 percent. Showers fall 35 percent of the years, but the sun shines at least eight years in ten.
July 26
Chances for highs in the 90s fall from yesterday’s 45 percent down to 30 percent, and 80s occur 60 percent of the time, with 70s ten percent. Rainfall on this date is moderate: storms pass through one day in three. Sunshine is common: 85 percent of the days bring clear to partly cloudy skies.
July 27
Today is one of only four July days on which there is only a 20 percent chance of a high above 90 degrees. Temperatures in the 80s can be expected 65 percent of the time. Seventies come on 15 percent of the afternoons. Rainfall often continues to lighten as the month comes to a close; a typical July 27th has a 30 percent chance for precipitation, 30 percent chance for completely cloudy skies.
July 28
Although the fourth high-pressure system of the month often comes through Ohio in the last days of July, temperatures and precipitation patterns often remain unaffected by it on the 28th. Thirty percent of the afternoons reach a high of 90 degrees, and 60 percent climb to the 80s, leaving only ten percent for 70s. Rainfall is similar to that recorded on the 28th: one day in three brings a shower. One day in three is overcast. When the last cool front of the month is especially strong, chances for lows in the 50s rise to 25 percent.
July 29
Highs reach into the 90s fifteen percent of the time on this date; 80s occur 65 percent, 70s twenty percent. Only one day in 15 is completely overcast, but thunderstorms come through one day in three. One night in three brings lows in the 50s; two out of three are in the 60s.
July 30
Today is hot, sunny, and dry eight years in ten. Temperatures rise to 90 or above 30 percent of the years, are in the 80s fifty-five percent, stay in the 70s just 15 percent. Rain occurs only once or twice in a decade. Fifteen percent of the nights are in the cool 50s.
July 31
Odds are good for a day just like yesterday: 30 percent chance for an afternoon in the 90s, fifty-five percent chance for one in the 80s, fifteen percent chance for 70s. Rain falls just two years in ten.