Seasonal swings are usually the biggest source of bill shock for newcomers, because the pleasant months lull you into a false baseline. In cold climates, winter heating can multiply energy bills to their annual peak, whether through gas, electricity, or district heating. In hot climates, summer air conditioning does the same to electricity. Places with both real winters and hot summers get two peaks a year, while mild coastal climates barely move.
Water bills can rise in summer with gardens and extra showers, and in some countries electricity or gas tariffs themselves change seasonally or with market prices, adding another layer. The practical defence is to budget on the annual average, not on your first month's bill; ask the landlord or previous tenant what the worst month looks like before you sign a lease, and check the insulation and the age of heating or cooling systems, which drive costs more than anything else.
Many utilities offer equalised or budget billing that spreads the yearly cost into even monthly payments, which is genuinely helpful for planning. And modest habits, like closing curtains against summer sun and sealing winter drafts, blunt the peaks considerably.