They say the problem could be worse in regional areas such as central Victoria, which experience more hot days in summer.

The risk is one of both heatstroke and COVID-19 transmission in the case of an outbreak, representatives warned.

Ambulance Victoria says its battling the risk with a range of options to manage heat stress, everything from icy poles to access to cool showers.

Read more: How our emergency services are protecting themselves in the pandemic

Victorian Ambulance Union secretary Danny Hill said heat stress and PPE breaches were a worry during the summer months.

Mr Hill said the effect of working in full PPE during hot summer weather would be "murderous".

He said the protective equipment was also less effective in hot weather, meaning an infection breach was more likely in the case of a COVID-19 outbreak.

Mr Hill called for strict protocols allowing members out of the heat after a maximum amount of time.

An Ambulance Victoria spokesperson said the organisation had a range of safety measures to protect its workforce from heat-related illness.

They said paramedics had access to cool showers at branches and hospital hubs, cool packs in all vehicles, uniform options such as shorts, access to cold water, electrolyte replacement products, icy poles at branches and Paramedic Support Hubs at hospitals.

The spokesperson confirmed paramedics wore protective eyewear, gloves and masks to all cases in response to COVID-19. To confirmed or suspected COVID-19 cases they wore a protective gown.

Read more: Long bushfires less likely this summer, high humidity forecast

This would be a lighter, breathable gown during summer, they said.

They said paramedics did not need to wear a protective gown for the vast majority of cases.

Ambulance Employees Australia Victoria organiser Lisa Harrup called for extra resources, so crews could alternate to minimise heat exposure.

Ms Harrup said this summer had the potential for a perfect health storm: a heatwave during a COVID-19 wave.

She said PPE was hot and restrictive, not allowing paramedics to rehydrate while wearing the mask, putting them at risk of heatstroke, heat exhaustion and dehydration.

Ms Harrup said extreme temperatures in the northern parts of the state were a concern, because she feared Ambulance Victoria was planning around Melbourne averages.

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