There was a weak La Nina this season, just as there was last. This one was a little weaker, and the temperature records went accordingly.
2016-2017 is still the warmest La Nina season, with 2017-18 a close second.
The 2017-2018 season saw a weak La Nina from October to March, according to the Oceanic Nino Index (ONI), as did 2016-2017. [ONI is the 3-month running mean of ERSST.v5 SST anomalies in the Niño 3.4 region (5°N-5°S, 120°-170°W)]
The La Nina waters for 2017-18 were slightly colder than the 2016-17 La Nina temperatures, going by the average ONI. And the global temperature was slightly colder too, according to UAH for the lower troposphere and NOAA for the surface.
I've only looked at the temperatures for NOAA (surface) and UAH (lower troposphere). Going by UAH's temperature for the global lower troposphere, including, now, June's, 2017-8 was the second-warmest La Nina year since UAH records begin in late 1978.
The UAH LT's ENSO's season's average for 2017-8, +0.33 C, was just slightly behind the 2016-7 average of +0.36 C.
La Nina seasons keep getting warmer (except, barely, this year, but then the La Nina, while weak, was stronger than 2016-2017). So do El Nino seasons. So do neutral seasons.
I should put up a pretty graphic here, but instead I'll link to this one, which is slightly out-of-date but communicates the essence.