I reckon that toms just have to get outside now, with potential protection if a frost beckons, because they really do need the light, not necessarily heat, to get going properly.
These longer days are so important for toms to develop - we've been so lucky with decent weather up to May in recent years, it's just this year that has chucked in the proverbial spanner!
Protection can be anything like a net even - I use clothes pegs to pin it down to anyything nearby, there's no rocket science involved!