I live in Central Texas and grew heat tolerant hybrids in 5
gallon buckets during jult and August and yes, 3 times a day was necessary
on those 100 degree days. I am trying some new stuff this yr with my soil.
Rather than using straight compost/potting soil mixes I am doing that with
some of the native clay soil we have here. Clay tends to retain mositure
better, altho it is not advisable to use in pots by itself for the reason
it
does not drain well. I am trying different ratios.

Don't discount peat moss. I grew tomatoes last year in containers, and
while it may not have been as hot as Texas, it was nearly 100 during the hot
months, at near-zero humidity. I used potting soil with a fair amount of
peat moss to hold the water, and I only had to water a couple of times per
week during the hot months.

steve