Cold / cloudy weather increases your engine's power which results in higher speeds, but the rev limit is still 9200. On most tracks, you have to lower the gearing in order to avoid hitting the rev limiter even before the end of the straights. Furthermore, you can usually use more tape by reducing revs a little.

Hotter temperatures mean less power => less top speed => less revs. You won't hit the rev limiter with thise conditions, but you won't reach your engine's peak power (which is at 8500+ RPM) either...