one swallow doesn't make a summer

one swallow does not make a summer

One piece of evidence does not mean that something is definitely the case or is going to happen. A reference to the migration of swallows that happens in the spring or early summer. A lot of things went right for us this year, but one swallow does not make a summer—we still have a long ways to go before our finances are back in order. A: "I'm really worried the boss is going to fire me. He said he really wasn't happy with my work lately!" B: "Calm down, one swallow doesn't make a summer."
See also: does, make, not, one, summer, swallow
Farlex Dictionary of Idioms.

one swallow doesn't make a summer

You say one swallow doesn't make a summer to mean that although something good has happened, the situation may not continue to be good, and you cannot rely on it. Sales in December were up about 1 percent, which of course, is good news. One swallow, however, doesn't make a summer and it remains to be seen whether they can maintain this growth in the difficult months ahead. Note: People often use the more literary phrase one swallow does not a summer make. One swallow does not a summer make, but a visit to the Hotel Metropole in Ipswich goes a long way to improving that city's reputation. Note: Swallows are a type of bird. The reference here is to the arrival of swallows in Europe at the beginning of summer, after spending the winter further south.
See also: make, one, summer, swallow
Collins COBUILD Idioms Dictionary, 3rd ed.

one swallow doesn't make a summer

a single fortunate event does not mean that what follows will also be good. proverb
1998 Spectator One swallow doesn't make a summer…nor one instance of police dereliction of duty, incompetence, laziness and stupidity a complete breakdown in law and order.
See also: make, one, summer, swallow
Farlex Partner Idioms Dictionary

one ˌswallow doesn’t make a ˈsummer

(saying) you must not take too seriously a small sign that something is happening or will happen in the future: ‘We got a big order from Sweden this morning. Things are getting better.’ ‘One swallow doesn’t make a summer, you know. Don’t be too optimistic.’
This expression refers to the fact that swallows (= small birds with a tail with two points) spend the winter in Africa but fly to northern countries for the summer.
See also: make, one, summer, swallow
Farlex Partner Idioms Dictionary
See also:
  • one swallow does not make a spring
  • one swallow does not make a summer
  • one swallow does not a spring make
  • one swallow does not a summer make
  • definitely
  • definitely not
  • Definitely not!
  • no doubt about it
  • (as) sure as eggs (is eggs)
  • swallow up
References in periodicals archive
The more wizened of the support are longtime subscribers to the notion that "One swallow doesn't make a summer", although it's more like "One Swallow doesn't even make for a nice day" regarding us, so we are expecting the lead-lined glove at any moment.
A VIEW FROM THE GALLOWGATE
"But everyone knows one swallow doesn't make a summer and, as Italy have learned, backing up a winning performance doesn't always come easily.
IRISH THE ACID TEST
One swallow doesn't make a summer and we won't be content to slip back into some of the bad habits that have seen us lose games this year.
Standards must not slip; JON WILKIN Super Saint writes for the ECHO
THEY say one swallow doesn't make a summer. Come to think of it, 400 million swallows wouldn't make a summer in this country.
Cowen is really hard to swallow
He should be reminded that one swallow doesn't make a summer and that prior to his arrival there was only one undetected murder in the force area, the situation today is quite different.
An insult to past police officers; yourLETTERS
One swallow doesn't make a summer, they say, but in the midst of the dol-drums, how many fine ballerinas does it take to give a festival wings?
INTERNATIONAL BALLET FESTIVAL OF MIAMI