This year's No Mow May campaign is coming up: How about taking part in some citizen science by signing up to the Plantlife Every Flower Counts campaign for 2020?
All you need to do is... not mow your grass for a month, then see how many flowers you get. This will really help all the pollinating insects to get going for the year. Even better, you can then leave some of the grass to get really long, only mowing after the end of July: You'll start to get some interesting different grasses and other plants flowering and will really help all sorts of creatures. If you're lucky, you may even find things like frogs in amongst the grass, as well as all sorts of bees, beetles and other minibeasts- perfect for doing some minibeast hunting.
And of course, if the rain stays away, longer grass with more species growing in it (especially clover) stays greener in dry weather than grass that's stressed with lots of mowing.
If you don't have a lawn or would like to help plant and minibeast species even more, you could take part in the Plantlife road verge campaign (you can then use your local verges to take part in the Every Flower Counts campaign!) and even better, email your local councillors or council parks department to ask for changes to mowing regimes in your local green spaces- many councils are really engaged with the climate emergency at the moment, so this is a great thing to be asking as it saves councils money and helps the environment- they're mostly just worried that residents won't like grass being left longer... so if you ask for it, that really helps them feel they can make a positive step for biodiversity- and will give you lovely flowers to look at!