Roach Risk Tracker
Estimate cockroach activity risk for a location from temperature, humidity and season — and what actually works if you have them.
Warmth is almost half the answer
The score is a weighted average of four readings, and the weights are nowhere near equal:
| Factor | Weight | Points it can move the score |
|---|---|---|
| Warmth | 0.45 | 45 |
| Humidity | 0.25 | 25 |
| Season | 0.18 | 18 |
| Recent rain | 0.12 | 12 |
Warmth is worth 3.8 times what recent rain is. If the number moves noticeably between two days, temperature is very likely the reason — and if you are wondering why yesterday's downpour barely shifted it, that is why.
And it stops responding at thirty degrees
Every reading is put through a ramp that clamps at both ends. Warmth runs from 12°C to 30°C:
| Temperature | Normalised | |
|---|---|---|
| 10°C | 0.000 | clamped |
| 12°C | 0.000 | clamped |
| 20°C | 0.444 | |
| 25°C | 0.722 | |
| 30°C | 1.000 | clamped |
| 35°C | 1.000 | clamped |
| 45°C | 1.000 | clamped |
A 45°C afternoon scores exactly the same as a 30°C one. That is defensible — past a point the conditions simply are favourable and more heat does not make them more so — but it means the bar sits pinned at 100% for a large part of the year in a hot climate, and the tool cannot tell a warm week from an extraordinary one. The same clamping applies to humidity (35–80%) and recent rain (0–12mm).
So the reading is a weather score offset by the calendar
The season factor is a cosine of the month, peaking in August in the northern hemisphere. On any given day it is a constant the weather cannot change, which fixes a band the score is unable to leave:
| Month | Season factor | Score can only run |
|---|---|---|
| February | 0.00 | 0 to 82 |
| May | 0.50 | 9 to 91 |
| August | 1.00 | 18 to 100 |
| November | 0.50 | 9 to 91 |
In February the reading can never exceed 82 however warm and humid it gets, and in August it can never drop below 18 however cold and dry. The band is always 82 points wide — the weather's whole share — sliding up and down the scale with the month. Every verdict remains reachable in every month, so the calendar tilts the answer without ever deciding it.
How to use
- Enter your location and conditions.
- Read the estimated activity risk.
- Address moisture and food access first.
- Call a professional for an established infestation.
Frequently asked questions
What conditions do cockroaches favour?
Warmth and moisture, above all. German cockroaches — the common indoor species — thrive in warm humid places with food and water access, which is why kitchens and bathrooms are where they establish. Activity rises sharply with temperature and falls in cold dry conditions.
What actually gets rid of them?
Removing what they need, then targeted treatment. Fixing leaks and reducing moisture, eliminating food access including pet food and rubbish, and sealing harbourage matters more than spraying. Gel baits are considerably more effective against German cockroaches than sprays, which can scatter a population rather than reduce it.
Why do foggers and bug bombs not work well?
Because they deposit insecticide on open surfaces while cockroaches shelter in cracks, voids and behind appliances. They can also drive a population deeper into a structure and into neighbouring units. Most pest management guidance advises against them for cockroaches specifically.
Does seeing one mean there are many?
Usually. Cockroaches are nocturnal and shelter-seeking, so daytime sightings in particular suggest a population large enough that individuals are being pushed out of preferred harbourage. One sighting is worth acting on rather than dismissing.
Are they a health risk?
Yes, and more than the unpleasantness suggests. Cockroach allergens are a well-documented trigger for asthma, particularly in children, and they can mechanically carry pathogens from waste to food surfaces. This is a genuine reason to treat an infestation rather than tolerate it.
When should I call a professional?
For anything established, and in a shared building almost always — a population moving between units cannot be solved from one flat. This page is general guidance and not pest control advice; a licensed operator can identify the species and treat what is actually there.
🌐 This tool looks up results using the free Open-Meteo weather API. The word you enter is sent to that service to fetch results; nothing is stored by this site.