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Is the reason that daily maximum temperatures are more consistent (as opposed to swinging between warm/hot and chilly) as well as warmer in July than in June in Northern Hemisphere locations because the jet stream has moved north in July as compared to June (and warm air masses are stronger and cold air masses are weaker in July)?
Is the reason that daily maximum temperatures are more consistent (as opposed to swinging between warm/hot and chilly) as well as warmer in July than in June in Northern Hemisphere locations because the jet stream has moved north in July as compared to June (and warm air masses are stronger and cold air masses are weaker in July)?
That pretty much should be it but there are areas and sometimes even we get 70s during the day and 90s another day in July and 50s at night.. (it can still fluctuate between hot and chilly).
Not to a great degree here in Tennessee. June highs are about 86 F and July highs average 90 F where I live. The lowest highs I've ever seen in each month are ~70 F. I will note that cool, even mildly cold nights can occur in June and are very rare in July.
Early June can feature some variation in weather, but after that it wont get interesting until mid September. An extreme example of boring summer weather is July 2010. Even though there were 30 days of 90 or above, the temperature never even reached 100!
Here in the interior of British Columbia, Canada, we get unsettled weather in May, June, and early July. Then the heat turns on around the 7th of July. We typically exceed 40 Celsius at least once every year (104 F). Everyone's climate is different though. I know that up the Yukon June is a nicer month.
The reason July tends to be hotter than June for most places is the same reason that solar noon is not the hottest part of the day. If there is more heat coming in from the sun than is being sent back into space, you get net heating, and as we all know it takes quite a few hours past noon for the sun's incoming energy to drop below the outgoing radiation.
net radiation = incoming solar (mostly visible light) - outgoing IR (infrared)
Late July is the most reliably warm time of the year. Though recently summers all seem to be warmer than average, a few years ago it was 6°C during solstice celebrations in late June. Air frost has also been officially recorded in all months except for July.
I have to admit that I was thinking more in terms of Montreal, where I'm from, than other places. (Of course, the climate can be different in each of June and July in other places.) The thing is, in a typical June (average high: 23C; average low: 14C) in Montreal, you have a lot of warm or even hot days but also quite a few cool, often cloudy days - the latter even in late June. For an example of a typical June, see June 2011. By contrast, in a typical July (average high: 26C; average low: 17C), the days are consistently warm or hot, with some exceptions. For an example of a typical July, see July 2011. And, at least in recent years, it seems that the shift from variability to consistency in daily highs takes place all the sudden when June turns into July, give or take a few days! So is the difference in the consistency or variability in daily highs owing to a shift in air masses, to a warming up of the land, or what? Or is it also because June is a month of transition between April-May and July-August whereas July is (along with August) high summer?
I also have to admit that I hope every July, particularly deep in July, to see at least one or two days reach a high of just 21-22C or below (and in many of the previous years you've had some cool days even in July), but these past few years have been disappointing in that regard. I have July of 2009, which was a cooler than normal July in Montreal, as a guide; but it seems that that particular July behaved somewhere between a typical June and a typical July.
Also the warmer water plays a role here in the coastal region of Germany.
While June can feature very cold days (with maximum temps in the low teens (C)/lower 50s F) it can also have very hot days with temps well in to the 30s°C/90°F.
Nights can be as warm as over 20°C/ 68°F but also as cold as 5°C/ 41°F.
In July, the highest temps can get up to 35°C/95°F, but the lowest maximums do rarely drop below 15°C/59°F even on its coldest days. The same is also valid for most of August here though.
Night temperatures in July and August are more consistent, rarely dropping below 10°C/50°F and the hottest nights also can be as warm as the low 20s°C/70s°F.
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